BEGIN:VCALENDAR VERSION:2.0 PRODID:-//linuxsoftware.nz//NONSGML Joyous v1.4//EN BEGIN:VEVENT SUMMARY:The GWverse and black-hole blues DTSTART:20210830T090000Z DTEND:20210830T180000Z DTSTAMP:20240329T082742Z UID:72e61732-8914-4447-87d6-63b9bf09fcdf SEQUENCE:7 CREATED:20210819T175522Z DESCRIPTION:In 2016\, a short time before the announcement of the first gr avitational-wave detection\, a cross-disciplinary initiative in Europe led to the establishment of the new CA16104 COST networking Action on Black h oles\, gravitational waves and fundamental physics (GWverse). GWverse\, c haired by Prof. Vitor Cardoso\, aims to maintain and consolidate leadershi p in black-hole physics and gravitational-wave science. The Action support s the training of the next generation of leaders in the field\, and the ve ry first “native” GW/multi-messenger astronomers\, ready to tackle the challenges of high-precision GW astronomy with ground and space-based det ectors.The fourth and final global meeting of the Action will be a hybrid meeting. The meeting will be remote (via Zoom)\, with its core programme t aking place in the afternoons\, from 30 Aug – 03 September 2021. However \, for those willing and able to be in Lisbon in person\, there will be ad ditional sessions in the morning in the wonderful Academy of Sciences of L isbon. A meeting of the Board of the Action is scheduled for the morning o f Aug 30.The first day of the meeting includes a public talk (at 16:00 PT) by well-known scientists Janna Levin (Columbia University) and Pedro G. F erreira (Oxford University). To join this public event\, please click htt ps://us02web.zoom.us/j/83173449837.Brief Bio of Janna Levin and Pedro G. F erreiraJanna Levin is the Tow Professor of physics and astronomy at Barnar d College of Columbia University. She has contributed to an understanding of black holes\, the cosmology of extra dimensions\, and gravitational wav es in the shape of spacetime. Among other prizes she has been named a Gugg enheim Fellow. She is also director of sciences at the cultural center Pio neer Works and the editor-in-chief of The Broadcast. Her previous books in clude How the Universe Got Its Spots and a novel\, A Madman Dreams of Turi ng Machines\, which won the PEN/Bingham Prize. Her book\, Black Hole Blues and Other Songs from Outer Space\, is the inside story on the discovery o f the century: the sound of spacetime ringing from the collision of two bl ack holes over a billion years ago. Her most recent book is Black Hole Sur vival Guide.Pedro G. Ferreira is Professor of Astrophysics at the Universi ty of Oxford. He studied and worked at Imperial College in London\, at the University of California at Berkeley and at CERN in Geneva. He has held v isiting positions at University of Edinburgh\, at the Albert Einstein Inst itute in Berlin and at Columbia University in New York. His area of expert ise is cosmology where he has pioneered research in the relic radiation le ft over from the Big Bang\, the nature of the dark Universe (such as dark matter and dark energy) and has led the way in studying alternatives to Ei nstein’s theory of General Relativity. He has published over 200 papers and has delivered over 100 talks at universities\, institutes and conferen ces all over Europe\, America\, Asia and Africa. Pedro has written extensi vely outside academia\, writing for Nature\, Science\, New Scientist\, Phy sics World\, Physics Today\, Scientific American\, Sky at Night\, CERN Cou rier\, BBC Focus\, The Guardian. His most recent book\, “The Perfect The ory: A Century of Geniuses and the Battle over General Relativity” has b een published in over 20 countries and was shortlisted for the 2014 Royal Society Winton Science Book Prize. LAST-MODIFIED:20210823T103520Z LOCATION:Academia de Ciências de Lisboa URL:http://df.vps.tecnico.ulisboa.pt/eventos/the-gwverse-and-black-hole-bl ues/ X-ALT-DESC;FMTTYPE=text/html:
In 2016\, a short time before the announcement of the firs t gravitational-wave detection\, a cross-disciplinary initiative in Europe led to the establishment of the new CA16104 COST networking Action on Black holes\, gravitational wav es and fundamental physics (GWverse). GWverse\, chaired by Prof. Vito r Cardoso\, aims to maintain and consolidate leadership in black-hole phys ics and gravitational-wave science. The Action supports the training of th e next generation of leaders in the field\, and the very first “native ” GW/multi-messenger astronomers\, ready to tackle the challenges of hig h-precision GW astronomy with ground and space-based detectors.
The fourth and final global meeting of the Action
will be a hybrid meeting. The meeting will be remote (via Zoom)\, with its
core programme taking place in the afternoons\, from 30 Aug – 03 Septem
ber 2021. However\, for those willing and able to be in Lisbon in person\,
there will be additional sessions in the morning in the wonderful Academy
of Sciences of Lisbon. A meeting of the Board of the Action is scheduled
for the morning of Aug 30.
The first day of the meeting includes a public talk (at 16:00 PT) by well-known scientists Janna Levin (Columbia University) and Pedro G. Ferreira (Oxford University ). To join this public event\, please click https://us02web.zoom.us/j/83173449837.
Brief Bio of Janna Levin and Pedro G. Ferreira
O Departamento de Física vai apresentar os novos membros à família DF. A cerimónia forma l de apresentação será virtual\, mas com direito a um copo de champagne celebratório real. Os novos colegas do nosso Departamento serão introd uzidos pelo coordenador da respectiva área\, e depois dir-nos-ão um pouc o acerca de si mesmos.
END:VEVENT BEGIN:VEVENT SUMMARY:The gravity of classical fields DTSTART:20210921T140000Z DTEND:20210921T170000Z DTSTAMP:20240329T082742Z UID:466c126b-2cb4-4c5e-a4c0-f99df41ad583 SEQUENCE:2 CREATED:20210912T083142Z DESCRIPTION:Rodrigo Vicente will defend his PhD work on "\;THE GRAVITY OF CLASSICAL FIELDS"\;\, done under supervision of Prof. Vítor Cardo so. The jury members are Richard Brito (Técnico\, referee)\, Katy Clough (Oxford\, referee)\, Lam Hui (Columbia University)\, José Natário (Té cnico) and Vítor Cardoso (Técnico). The committee is presided by José L emos (Técnico). LAST-MODIFIED:20210912T085148Z LOCATION:Técnico URL:http://df.vps.tecnico.ulisboa.pt/eventos/the-gravity-of-classical-fiel ds/ X-ALT-DESC;FMTTYPE=text/html:Rodrigo Vicente wil l defend his PhD work on "\;THE GRAVITY OF CLASSICAL FIELDS"\;\, d one under supervision of Prof. Vítor Cardoso. The jury members are Richar d Brito (Técnico\, referee)\, Katy Clough (Oxford\, referee)\, Lam Hui (C olumbia University)\, José Natário (Técnico) and Vítor Cardoso (Téc nico). The committee is presided by José Lemos (Técnico).
END:VEVENT BEGIN:VEVENT SUMMARY:Recepção às famílias DTSTART:20211002T090000Z DTEND:20211002T130000Z DTSTAMP:20240329T082742Z UID:412a0b77-0d73-480e-a96e-479357fbe634 SEQUENCE:1 CREATED:20211002T152820Z DESCRIPTION:O Departamento de Física organiza uma recepção às família s dos estudantes que este ano ingressaram em Física. O curso de Física e stá mais uma vez no topo das preferências dos alunos mais talentosos do país\, muitos dos quais são oriendos dos mais variados pontos de Portuga l. O Professor Luís Oliveira e Silva fará uma pequena visita guiada à E scola\, passando pelos principais pontos de referência e esclarecendo qua isquer dúvida. Bem-vindos a todos ao DF. LAST-MODIFIED:20211002T152820Z LOCATION:Campus da Alameda URL:http://df.vps.tecnico.ulisboa.pt/eventos/recep%C3%A7%C3%A3o-%C3%A0s-fa m%C3%ADlias/ X-ALT-DESC;FMTTYPE=text/html:O Departamento de F ísica organiza uma recepção às famílias dos estudantes que este ano i ngressaram em Física. O curso de Física está mais uma vez no topo das p referências dos alunos mais talentosos do país\, muitos dos quais são o riendos dos mais variados pontos de Portugal. O Professor Luís Oliveira e Silva fará uma pequena visita guiada à Escola\, passando pelos principa is pontos de referência e esclarecendo quaisquer dúvida. Bem-vindos a to dos ao DF.
END:VEVENT BEGIN:VEVENT SUMMARY:Recepção aos novos alunos DTSTART:20211015T170000Z DTEND:20211015T180000Z DTSTAMP:20240329T082742Z UID:daaf488f-9e6d-40bb-a4c1-b5c30123be4e SEQUENCE:6 CREATED:20210820T184354Z DESCRIPTION:O DF vai dar as boas vindas aos novos alunos do LEFT e MEFT\, dia 15 de Outubro. A recepção vai incluir uma descrição do departament o e dos eventos mais extraordinários dos últimos anos. Durante este even to\, vamos ouvir ex-alunos do DF\, incluindo Helvi Witek (actualmente prof essora na Universidade de Urbana-Illinois nos Estados Unidos)\, e alunos a ctuais como o José Figueiredo. Vamos convidar o NFIST a mostrar-se e as n ovas caras do DF a apresentarem-se. E temos uma surpresa para todos. LAST-MODIFIED:20221021T094106Z LOCATION:Salão Nobre\, Edificio Central URL:http://df.vps.tecnico.ulisboa.pt/eventos/recep%C3%A7%C3%A3o-aos-novos- alunos/ X-ALT-DESC;FMTTYPE=text/html:
O DF vai dar a
s boas vindas aos novos alunos do LEFT e MEFT\, dia 15 de Outubro. A recep
ção vai incluir uma descrição do departamento e dos eventos mais extra
ordinários dos últimos anos. Durante este evento\, vamos ouvir ex-alunos
do DF\, incluindo Helvi Witek (actualmente professora na Universidade de
Urbana-Illinois nos Estados Unidos)\, e alunos actuais como o José Figuei
redo. Vamos convidar o NFIST a mostrar-se e as novas caras do DF a apresen
tarem-se. E temos uma surpresa para todos.
The theory of
a complex scalar field minimally coupled to gravity allows for amusing sta
tionary configurations that defy common intuition built upon our knowledge
of more conservative compact objects. Upon rotation\, the topology of the
scalar field changes and the solution possesses an offcenter distribution
of energy density. In turn\, the metric potentials behave nonmotonically
with increasing radial coordinate\, deviating considerably from external K
err. In this talk we shall explore the spacetime structure of rotating bos
on stars (BSs) and Kerr black holes with scalar hair (KBHsSH) and address
peculiar properties of circular orbits on their equatorial plane\, as well
as some astrophysical implications to accretion discs and inspirals. Furt
hermore\, by attempting a fluid description of the complex scalar field\,
we will unveil a strange connection between a BS co-moving observer and th
e synchronization condition for KBHsH.
(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecn ico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:Scalar Mixing in New Physics Models DTSTART:20211117T090000Z DTEND:20211117T110000Z DTSTAMP:20240329T082742Z UID:9203b1eb-caa7-48f0-a76a-2493f67e185b SEQUENCE:1 CREATED:20211115T111211Z DESCRIPTION: LAST-MODIFIED:20211115T111211Z LOCATION: URL:http://df.vps.tecnico.ulisboa.pt/eventos/scalar-mixing-in-new-physics- models/ END:VEVENT BEGIN:VEVENT SUMMARY:Experimental investigation and kinetic... DTSTART:20211118T140000Z DTEND:20211118T160000Z DTSTAMP:20240329T082742Z UID:4ddb541f-8eec-46c9-849e-5ac4a5a1f6e5 SEQUENCE:1 CREATED:20211117T152008Z DESCRIPTION: Experimental investigation and kinetic modeling of CO2-CH4 pl asmas (mestrado) LAST-MODIFIED:20211117T152008Z LOCATION:Sala C10\, Pavilhão Central\, 1º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/experimental-investigation-an d-kinetic/ X-ALT-DESC;FMTTYPE=text/html:Experimental inves tigation and kinetic modeling of CO2-CH4 plasmas (mestrado)
END:VEVENT BEGIN:VEVENT SUMMARY:Towards a distributed magnetic tactile... DTSTART:20211118T140000Z DTEND:20211118T160000Z DTSTAMP:20240329T082742Z UID:cd8b4843-ad58-4d17-a4b3-0302cdd14f73 SEQUENCE:1 CREATED:20211117T152714Z DESCRIPTION: Towards a distributed magnetic tactile sensor network for fle xible skin (mestrado) LAST-MODIFIED:20211117T152714Z LOCATION: URL:http://df.vps.tecnico.ulisboa.pt/eventos/towards-a-distributed-magneti c-tactile/ X-ALT-DESC;FMTTYPE=text/html:Towards a distribu ted magnetic tactile sensor network for flexible skin (mestrado)
END:VEVENT BEGIN:VEVENT SUMMARY:Confronting Multi-Higgs models with experiment: The Search for Und errated and Understudied Signals (mestrado) DTSTART:20211123T083000Z DTEND:20211123T110000Z DTSTAMP:20240329T082742Z UID:f0a763c1-17c7-41c2-a1c7-65880ab68f00 SEQUENCE:1 CREATED:20211122T105404Z DESCRIPTION: LAST-MODIFIED:20211122T105404Z LOCATION:https://videoconf-colibri.zoom.us/j/87847848381?pwd=NTRCTXpzTkM4Q S9QcDM5LzZoRWwydz09 URL:http://df.vps.tecnico.ulisboa.pt/eventos/confronting-multi-higgs-model s-with-experiment-the-search-for-underrated-and-understudied-signals-mestr ado/ END:VEVENT BEGIN:VEVENT SUMMARY:Some Theoretical Aspects of Multi-Higgs Doublet Models DTSTART:20211123T103000Z DTEND:20211123T130000Z DTSTAMP:20240329T082742Z UID:51141da5-6759-41ea-898a-fcd572c47756 SEQUENCE:1 CREATED:20211122T104917Z DESCRIPTION: LAST-MODIFIED:20211122T104917Z LOCATION:https://videoconf-colibri.zoom.us/j/87847848381?pwd=NTRCTXpzTkM4Q S9QcDM5LzZoRWwydz09 URL:http://df.vps.tecnico.ulisboa.pt/eventos/some-theoretical-aspects-of-m ulti-higgs-doublet-models/ END:VEVENT BEGIN:VEVENT SUMMARY:Polarimetric Studies of Galaxies DTSTART:20211123T170000Z DTEND:20211123T190000Z DTSTAMP:20240329T082742Z UID:a7f74870-4647-443e-8199-3d72334bc538 SEQUENCE:1 CREATED:20211110T151920Z DESCRIPTION: LAST-MODIFIED:20211110T151920Z LOCATION:Sala de Formação Avançada do DF - piso 2 URL:http://df.vps.tecnico.ulisboa.pt/eventos/polarimetric-studies-of-galax ies/ END:VEVENT BEGIN:VEVENT SUMMARY:Testing General Relativity at the galactic centre DTSTART:20211124T100000Z DTEND:20211124T110000Z DTSTAMP:20240329T082742Z UID:d66a6740-3125-433f-ab5e-b460d6bec376 SEQUENCE:4 CREATED:20210909T140029Z DESCRIPTION:PhD student Arianna Foschi will discuss her thesis work on str ong-field gravity. The thesis supervisor is Prof. Vítor Cardoso. The Comm ission accompanying the PhD work (CAT) is composed of members: V. Cardoso\ , P. Garcia\, A. Maselli\, and I. Lopes (president). LAST-MODIFIED:20211112T113148Z LOCATION:seminar room\, physics department URL:http://df.vps.tecnico.ulisboa.pt/eventos/testing-general-relativity-at -the-galactic-centre/ X-ALT-DESC;FMTTYPE=text/html:PhD student Arianna Foschi will discuss her thesis work on strong-field gravity. The thesis s upervisor is Prof. Vítor Cardoso. The Commission accompanying the PhD wor k (CAT) is composed of members: V. Cardoso\, P. Garcia\, A. Maselli\, and I. Lopes (president).
END:VEVENT BEGIN:VEVENT SUMMARY:Voltage dynamics and statistics in balanced networks DTSTART:20211124T143000Z DTEND:20211124T160000Z DTSTAMP:20240329T082742Z UID:43dbc04f-5d06-4286-87ea-e09f359ae8cb SEQUENCE:3 CREATED:20211123T164130Z DESCRIPTION: LAST-MODIFIED:20211124T145527Z LOCATION:https://videoconf-colibri.zoom.us/j/85113082888?pwd=dS9PRjh2WUVTc ER3ZHV6MUpESnBNQT09 URL:http://df.vps.tecnico.ulisboa.pt/eventos/voltage-dynamics-and-statisti cs-in-balanced-networks/ END:VEVENT BEGIN:VEVENT SUMMARY:Lyapunov-Governed Magnitude-Independent Average Fidelity Decay in a Classically Mixed Two-Spin System DTSTART:20211125T100000Z DTEND:20211125T120000Z DTSTAMP:20240329T082742Z UID:0c1ff6fa-c6fe-44de-97bf-192d70d4ec3b SEQUENCE:1 CREATED:20211124T150147Z DESCRIPTION: LAST-MODIFIED:20211124T150147Z LOCATION:https://videoconf-colibri.zoom.us/j/87954064199?pwd=Z0lsZGthb1ZKa Dg3TExTR2tqeTZ5dz09 URL:http://df.vps.tecnico.ulisboa.pt/eventos/lyapunov-governed-magnitude-i ndependent-average-fidelity-decay-in-a-classically-mixed-two-spin-system/ END:VEVENT BEGIN:VEVENT SUMMARY:From light-front wave functions to parton distribution functions DTSTART:20211125T100000Z DTEND:20211125T120000Z DTSTAMP:20240329T082742Z UID:2c01e66b-5499-4c3f-aed2-af1221b29322 SEQUENCE:2 CREATED:20211124T145902Z DESCRIPTION: LAST-MODIFIED:20211124T155120Z LOCATION:https://videoconf-colibri.zoom.us/j/83168427728?pwd=MnhiWS9aOHY3Z WFGbEIrNkZLdndsZz09 URL:http://df.vps.tecnico.ulisboa.pt/eventos/from-light-front-wave-functio ns-to-parton-distribution-functionsfrom-light-front-wave-functions-to-part on-distribution-functions/ END:VEVENT BEGIN:VEVENT SUMMARY:Probing multiparticle production properties of the first ultra-hig h energy cosmic ray-Air interaction in Extensive Air Showers with low muon content DTSTART:20211125T113000Z DTEND:20211125T130000Z DTSTAMP:20240329T082742Z UID:384b49f2-2387-4847-aeca-49f1351ec222 SEQUENCE:3 CREATED:20211123T164357Z DESCRIPTION: LAST-MODIFIED:20211126T163012Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/probing-multiparticle-product ion-properties-of-the-first-ultra-high-energy/ END:VEVENT BEGIN:VEVENT SUMMARY:The large D limit of General Relativity DTSTART:20211125T143000Z DTEND:20211125T160000Z DTSTAMP:20240329T082742Z UID:4fcf6a7e-c744-48e0-b846-1a9660729fe9 SEQUENCE:2 CREATED:20211122T101435Z DESCRIPTION: Speaker: Raimon Luna (CENTRA)Title: "\;The large D limit of General Relativity"\;Abstract:In this seminar I will give an overvi ew of the recent developments in the Large D limit of gravity. In this app roach\, we explore the limit General Relativity as the number of dimension s grows very large\, which allows us to perform perturbative analysis with asymptotic expansions in powers of 1/D\, with D being the dimension of sp acetime. This makes it possible to access analytically (or with very modes t numerical techniques) the physics of black holes\, both in D=4 and in hi gher dimensions. In particular\, I will focus on the effective theory for black holes with extended directions (mainly black strings and black brane s) which has been used to recover the critical dimension of black strings\ , and most importantly to predict violations of Penrose'\;s Weak Cosmi c Censorship conjecture in black hole mergers through the so-called blobol ogy formalism.For those who cannot attend the seminar in person\, we will also broadcast it through zoom: https://videoconf-colibri.zoom.us/j/850370 94360?pwd=d0dPV2tUdlQvNy80K1g1UzljdlUvUT09Contact organizer for password. Organizer: Alex Vano-Vinuales (alex.vano.vinuales@tecnico.ulisboa.pt) LAST-MODIFIED:20211122T104610Z LOCATION:Sala de seminários do DF URL:http://df.vps.tecnico.ulisboa.pt/eventos/the-large-d-limit-of-general- relativity/ X-ALT-DESC;FMTTYPE=text/html:
Speaker: Raimon Luna (CENTRA)
Title: "\;The large D limit of General Relativity"\
;
Abstract:
In this seminar I will g
ive an overview of the recent developments in the Large D limit of gravity
. In this approach\, we explore the limit General Relativity as the number
of dimensions grows very large\, which allows us to perform perturbative
analysis with asymptotic expansions in powers of 1/D\, with D being the di
mension of spacetime. This makes it possible to access analytically (or wi
th very modest numerical techniques) the physics of black holes\, both in
D=4 and in higher dimensions. In particular\, I will focus on the effectiv
e theory for black holes with extended directions (mainly black strings an
d black branes) which has been used to recover the critical dimension of b
lack strings\, and most importantly to predict violations of Penrose'\
;s Weak Cosmic Censorship conjecture in black hole mergers through the so-
called blobology formalism.
For those wh
o cannot attend the seminar in person\, we will also broadcast it through
zoom: https://videoconf-colibri.zoom.us/j/85037094360
?pwd=d0dPV2tUdlQvNy80K1g1UzljdlUvUT09
Contact organizer for passwo
rd.
Organizer: Alex Vano-Vinuales (alex.vano.vinuales@tecnico.ulisboa.pt)
END:VEVENT BEGIN:VEVENT SUMMARY:A novel energy reconstruction for high-energy gamma-ray wide field of view observatories DTSTART:20211125T150000Z DTEND:20211125T170000Z DTSTAMP:20240329T082742Z UID:32ba8e44-3526-4cf5-b2d4-a73f0181e6d6 SEQUENCE:1 CREATED:20211124T145650Z DESCRIPTION: LAST-MODIFIED:20211124T145650Z LOCATION:https://videoconf-colibri.zoom.us/j/83608217848?pwd=OE1FeXd3QWZQe DZsMjVOcms4NWsyQT09 URL:http://df.vps.tecnico.ulisboa.pt/eventos/a-novel-energy-reconstruction -for-high-energy-gamma-ray-wide-field-of-view-observatories/ END:VEVENT BEGIN:VEVENT SUMMARY:Growth of noble metal Au-Nano particles into selected dielectric m atrixes DTSTART:20211125T153000Z DTEND:20211125T163000Z DTSTAMP:20240329T082742Z UID:2fa1e46d-13fa-4c30-be79-f73dcdc78bee SEQUENCE:2 CREATED:20211124T150031Z DESCRIPTION: LAST-MODIFIED:20211126T162814Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/growth-of-noble-metal-au-nano -particles-into-selected-dielectric-matrixes/ END:VEVENT BEGIN:VEVENT SUMMARY:Evolution of Dipolar Boson Stars and Head-on Collisions of Spheric al Boson Stars DTSTART:20211126T140000Z DTEND:20211126T160000Z DTSTAMP:20240329T082742Z UID:5c9160ac-4893-48e6-ac3f-a919f10f1c4a SEQUENCE:1 CREATED:20211125T095010Z DESCRIPTION: LAST-MODIFIED:20211125T095010Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/evolution-of-dipolar-boson-st ars-and-head-on-collisions-of-spherical-boson-stars/ END:VEVENT BEGIN:VEVENT SUMMARY:Cr-doped β-Ga2O3 for radiation detection DTSTART:20211129T110000Z DTEND:20211129T130000Z DTSTAMP:20240329T082742Z UID:f456d75f-b9d0-438a-b70a-5511188ed86f SEQUENCE:3 CREATED:20211129T113205Z DESCRIPTION: LAST-MODIFIED:20211129T113354Z LOCATION:Sala de Formação Avançada do DF (Sala 2-8.11 - 2º Piso do Pav ilhão de Física) URL:http://df.vps.tecnico.ulisboa.pt/eventos/cr-doped-%CE%B2-ga2o3-for-rad iation-detection/ END:VEVENT BEGIN:VEVENT SUMMARY:A hidden\, heavier resonance of the Higgs field DTSTART:20211130T160000Z DTEND:20211130T180000Z DTSTAMP:20240329T082742Z UID:c68387b6-39ae-47ca-b385-a04d0621dd36 SEQUENCE:4 CREATED:20211130T091942Z DESCRIPTION:Spontaneous symmetry breaking is an essential ingredient of th e Standard Model. While Goldstone bosons are well understood\, stillthe ul timate dynamical origin of the phenomenon is not entirely clear. Given t his uncertainty\, one may wonder about the present view that the Higgs-fie ld propagator has only one pole at 125 GeV. In fact\, depending on the des cription of symmetry breaking\, the effective potential\, besides the mass scale describing its quadratic shape at the minima\, could exhibit anothe r mass scale associated with the zero-point energy\, which determines its depth. Lattice simulations of the propagator are consistent with this two- mass structure and can be used to predict a new resonance around 700 GeV. In spite of its large mass\, however\, the heavier state would couple to l ongitudinal Ws with the same typical strength of the low-mass state and th us represent a relatively narrow resonance. In this way\, such a hypotheti cal resonance would naturally fit with some excess of 4-lepton events obse rved by ATLAS around 680 GeV. Available CMS data in the same region\, when grouped in bins of 30 GeV as done by ATLAS\, are also consistent with thi s interpretation. Implications of this two-mass structure for radiative co rrections will also be discussed. LAST-MODIFIED:20211130T143039Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/a-hidden-heavier-resonance-of -the-higgs-field/ X-ALT-DESC;FMTTYPE=text/html:Spontaneous symmetr y breaking is an essential ingredient of the Standard Model. While Goldsto ne bosons are well understood\, stillthe ultimate dynamical origin of th e phenomenon is not entirely clear. Given this uncertainty\, one may wonde r about the present view that the Higgs-field propagator has only one pole at 125 GeV. In fact\, depending on the description of symmetry breaking\, the effective potential\, besides the mass scale describing its quadratic shape at the minima\, could exhibit another mass scale associated with th e zero-point energy\, which determines its depth. Lattice simulations of t he propagator are consistent with this two-mass structure and can be used to predict a new resonance around 700 GeV. In spite of its large mass\, ho wever\, the heavier state would couple to longitudinal Ws with the same ty pical strength of the low-mass state and thus represent a relatively narro w resonance. In this way\, such a hypothetical resonance would naturally f it with some excess of 4-lepton events observed by ATLAS around 680 GeV. A vailable CMS data in the same region\, when grouped in bins of 30 GeV as d one by ATLAS\, are also consistent with this interpretation. Implications of this two-mass structure for radiative corrections will also be discusse d.
END:VEVENT BEGIN:VEVENT SUMMARY:Plasmonic instabilities in two-dimensional Dirac materials DTSTART:20211130T160000Z DTEND:20211130T180000Z DTSTAMP:20240329T082742Z UID:f83c516d-5775-49b7-b1f2-3c0147da56eb SEQUENCE:2 CREATED:20211130T143451Z DESCRIPTION: The generation of coherent terahertz radiation is an outstan ding challenge at both scientific and technological levels. In one hand\, the quest for table-top THz solutions based on integrated-circuit technolo gy puts graphene and other bi-dimensional in the run\; on the other\, plas ma instabilities in bi-dimensional materials are an appealing mechanism fo r the production of low-power coherent THz signals. In this talk\, we disc uss how to produce plasmonic instabilities in graphene field-effect transi stors based on electronic injection only. LAST-MODIFIED:20211130T144348Z LOCATION:Auditorium/Room 9 @ INESC URL:http://df.vps.tecnico.ulisboa.pt/eventos/plasmonic-instabilities-in-tw o-dimensional-dirac-materials/ X-ALT-DESC;FMTTYPE=text/html:
The generation of coherent tera hertz radiation is an outstanding challenge at both scientific and technol ogical levels. In one hand\, the quest for table-top THz solutions based o n integrated-circuit technology puts graphene and other bi-dimensional in the run\; on the other\, plasma instabilities in bi-dimensional materials are an appealing mechanism for the production of low-power coherent THz si gnals. In this talk\, we discuss how to produce plasmonic instabilities in graphene field-effect transistors based on electronic injection only.
END:VEVENT BEGIN:VEVENT SUMMARY:A First Sample of Dust Attenuation Laws for DES Galaxies DTSTART:20211130T170000Z DTEND:20211130T190000Z DTSTAMP:20240329T082742Z UID:a588b1c6-4263-4631-b513-fb2b2c232a21 SEQUENCE:2 CREATED:20211129T112848Z DESCRIPTION: LAST-MODIFIED:20211129T113407Z LOCATION:Sala de Formação Avançada do DF (Sala 2-8.11 - 2º Piso do Pav ilhão de Física) URL:http://df.vps.tecnico.ulisboa.pt/eventos/a-first-sample-of-dust-attenu ation-laws-for-des-galaxies/ END:VEVENT BEGIN:VEVENT SUMMARY:Charged dark matter DTSTART:20211202T143000Z DTEND:20211202T160000Z DTSTAMP:20240329T082742Z UID:90a3a221-0fcb-4e29-a250-f9775aaaedb2 SEQUENCE:2 CREATED:20211129T112042Z DESCRIPTION:Is it possible to have long range forces competing with gravit y at large\, astrophysical and cosmological scales? The unknown nature of the dark sector allows to speculate on this possibility. In this talk I wi ll present a model in which a universally charged dark matter component ha s this property. This scenario comes equipped with a natural screening mec hanism a là K-mouflage thus avoiding traditional constraints on this kind of forces. After introducing the model properties\, I will focus on its p henomenology. In particular\, I will show how an inhomogeneous cosmologica l model is dynamically generated and explore its connection with the Hubbl e tension and astrophysical bodies dynamics. Finally\, I will briefly disc uss how further constraints on the model can be cast by considering the li near response of charged objects under an external static field. LAST-MODIFIED:20211129T113555Z LOCATION:Sala de Seminários do DF (2-8.3) 2º Piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/charged-dark-matter/ X-ALT-DESC;FMTTYPE=text/html:Is it possible to h
ave long range forces competing with gravity at large\, astrophysical and
cosmological scales? The unknown nature of the dark sector allows to specu
late on this possibility. In this talk I will present a model in which a u
niversally charged dark matter component has this property. This scenario
comes equipped with a natural screening mechanism a là K-mouflage thus av
oiding traditional constraints on this kind of forces. After introducing t
he model properties\, I will focus on its phenomenology. In particular\, I
will show how an inhomogeneous cosmological model is dynamically generate
d and explore its connection with the Hubble tension and astrophysical bod
ies dynamics. Finally\, I will briefly discuss how further constraints on
the model can be cast by considering the linear response of charged object
s under an external static field.
In 1887 Michelson a
nd Morley tried to observe in laboratory the "\;ether wind"\; by m
easuring a small difference in the velocity of two perpendicular light bea
ms. Their measurements being much smaller than the classical expectations\
, the experiment was interpreted as a null result. This was crucial for th
e first pioneering formulations of the relativistic effects and represents
a fundamental step in the history of science. Since then\, more and more
precise repetitions of that original experiment have been performed and th
e standard conclusion has been always the same: no genuine ether wind has
ever been detected.
However\, if the vel ocity of light in the various interferometers is not exactly the same para meter "\;c"\; of Lorentz transformations nothing would prevent in principle a non-zero effect. For instance\, in a gaseous medium the small fraction of refracted light could keep track of the motion of matter with respect to some preferred reference frame. Starting from this observation\ , there is now a new interpretation where the small irregular residuals ob served in laboratory show surprising correlations with the direct observat ions of the Cosmic Microwave Background (CMB) with satellites in space. Th is opens the possibility of finally linking the CMB with a fundamental ref erence system for relativity with substantial implications for the interpr etation of non-locality in the quantum theory. The Colloquium will focus on the essential aspects of this research with brief historical notes on some leading scientists involved in these measurements.
END:VEVENT BEGIN:VEVENT SUMMARY:Novel Optimization Strategies for Clinical FLASH Proton Therapy. E valuation on stereotactic lung treatment plans DTSTART:20211203T090000Z DTEND:20211203T110000Z DTSTAMP:20240329T082742Z UID:a841c813-30dc-427d-a697-7c40529ff949 SEQUENCE:2 CREATED:20211202T091558Z DESCRIPTION: (Contactar Ana Bela Cardoso para password)ana.bela.cardoso@t ecnico.ulisboa.pt LAST-MODIFIED:20211202T092717Z LOCATION:https://videoconf-colibri.zoom.us/j/83608217848?pwd=OE1FeXd3QWZQe DZsMjVOcms4NWsyQT09 URL:http://df.vps.tecnico.ulisboa.pt/eventos/novel-optimization-strategies -for-clinical-flash-proton-therapy-evaluation-on-stereotactic-lung-treatme nt-plans/ X-ALT-DESC;FMTTYPE=text/html:
(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecnico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:Towards time ordered parton showers DTSTART:20211206T090000Z DTEND:20211206T110000Z DTSTAMP:20240329T082742Z UID:99b35697-0d26-4ae2-9909-e557de602c22 SEQUENCE:2 CREATED:20211203T160336Z DESCRIPTION:https://videoconf-colibri.zoom.us/j/83608217848?pwd=OE1FeXd3QW ZQeDZsMjVOcms4NWsyQT09(Contactar Ana Bela Cardoso para password)ana.bela.c ardoso@tecnico.ulisboa.pt LAST-MODIFIED:20211206T210047Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/towards-time-ordered-parton-s howers/ X-ALT-DESC;FMTTYPE=text/html:
https://videoc
onf-colibri.zoom.us/j/83608217848?pwd=OE1FeXd3QWZQeDZsMjVOcms4NWsyQT09
(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecnico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:Modular Symmetries and the Flavour Problem DTSTART:20211206T093000Z DTEND:20211206T110000Z DTSTAMP:20240329T082742Z UID:0e71057a-5920-48e6-ae36-980008a01b3b SEQUENCE:1 CREATED:20211203T160830Z DESCRIPTION: (Contactar Ana Bela Cardoso para password)ana.bela.cardoso@t ecnico.ulisboa.pt LAST-MODIFIED:20211203T160830Z LOCATION:https://videoconf-colibri.zoom.us/j/87847848381?pwd=NTRCTXpzTkM4Q S9QcDM5LzZoRWwydz09 URL:http://df.vps.tecnico.ulisboa.pt/eventos/modular-symmetries-and-the-fl avour-problem/ X-ALT-DESC;FMTTYPE=text/html:
(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecnico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:End-to-end simulation of satellite based quantum key distribution DTSTART:20211206T160000Z DTEND:20211206T180000Z DTSTAMP:20240329T082742Z UID:35c2d71f-26f5-46db-99a6-cafc19bce06d SEQUENCE:1 CREATED:20211203T161055Z DESCRIPTION: (Contactar Ana Bela Cardoso para password)ana.bela.cardoso@t ecnico.ulisboa.pt LAST-MODIFIED:20211203T161055Z LOCATION:https://videoconf-colibri.zoom.us/j/87311935352?pwd=aThwKzFvMXFzY WpMZXIzK05yYnc1UT09 URL:http://df.vps.tecnico.ulisboa.pt/eventos/end-to-end-simulation-of-sate llite-based-quantum-key-distribution/ X-ALT-DESC;FMTTYPE=text/html:
(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecnico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:Frequency resolved optical gating for ultrashort mid-infrared lase r pulses DTSTART:20211207T093000Z DTEND:20211207T113000Z DTSTAMP:20240329T082742Z UID:e4ab9dcc-723d-41ce-a2ea-c208288ffc3f SEQUENCE:4 CREATED:20211206T151346Z DESCRIPTION:(Contactar Ana Bela Cardoso para password)ana.bela.cardoso@tec nico.ulisboa.pt LAST-MODIFIED:20211207T155512Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/frequency-resolved-optical-ga ting-for-ultrashort-mid-infrared-laser-pulses/ X-ALT-DESC;FMTTYPE=text/html:(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecnico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:Development of a trigger system for the ESTHER Shock Tube Spectros copy/Streak-Camera Diagnostic DTSTART:20211207T160000Z DTEND:20211207T180000Z DTSTAMP:20240329T082742Z UID:8fa922fb-9343-4f44-8a85-490d9c5d9cdb SEQUENCE:2 CREATED:20211206T151139Z DESCRIPTION:(Contactar Ana Bela Cardoso para password)ana.bela.cardoso@tec nico.ulisboa.pt LAST-MODIFIED:20211207T004031Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/development-of-a-trigger-syst em-for-the-esther-shock-tube-spectroscopystreak-camera-diagnostic/ X-ALT-DESC;FMTTYPE=text/html:(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecnico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:Development of a magnetic camera for barcode and QR magnetic Ident ification tag readout DTSTART:20211207T163000Z DTEND:20211207T180000Z DTSTAMP:20240329T082742Z UID:4de868b5-5e0f-4811-b0e4-be64c2a0616b SEQUENCE:2 CREATED:20211203T160611Z DESCRIPTION:(Contactar Ana Bela Cardoso para password)ana.bela.cardoso@tec nico.ulisboa.pt LAST-MODIFIED:20211207T214545Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/development-of-a-magnetic-cam era-for-barcode-and-qr-magnetic-identification-tag-readout/ X-ALT-DESC;FMTTYPE=text/html:(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecnico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:Nonlinear optics with ultrashort mid-infrared laser pulses DTSTART:20211209T100000Z DTEND:20211209T120000Z DTSTAMP:20240329T082742Z UID:8a60263c-4766-4ff8-804f-90234be3682e SEQUENCE:2 CREATED:20211206T151514Z DESCRIPTION:(Contactar Ana Bela Cardoso para password)ana.bela.cardoso@tec nico.ulisboa.pt LAST-MODIFIED:20211207T004420Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/nonlinear-optics-with-ultrash ort-mid-infrared-laser-pulses/ X-ALT-DESC;FMTTYPE=text/html:(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecnico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:PALS – Setup optimisation and application to macromolecular mate rials characterisation DTSTART:20211209T100000Z DTEND:20211209T120000Z DTSTAMP:20240329T082742Z UID:de392951-69cb-4335-9df1-3848f5469057 SEQUENCE:2 CREATED:20211207T151716Z DESCRIPTION:(Contactar Ana Bela Cardoso para password)ana.bela.cardoso@tec nico.ulisboa.pt LAST-MODIFIED:20211207T153347Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/pals-setup-optimisation-and-a pplication-to-macromolecular-materials-characterisation/ X-ALT-DESC;FMTTYPE=text/html:(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecnico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:A Computational Model for Radiotherapy Studies with Proton and Car bon ion Mini-Beams DTSTART:20211209T140000Z DTEND:20211209T160000Z DTSTAMP:20240329T082742Z UID:4e2c12d7-f418-47cc-b8c9-66597fdc4541 SEQUENCE:3 CREATED:20211207T152309Z DESCRIPTION:(Contactar Ana Bela Cardoso para password)ana.bela.cardoso@tec nico.ulisboa.pt LAST-MODIFIED:20211207T153249Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/a-computational-model-for-rad iotherapy-studies-with-proton-and-carbon-ion-mini-beams/ X-ALT-DESC;FMTTYPE=text/html:(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecnico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:Classical and Quantum simulation of Extreme Plasma Physics DTSTART:20211209T140000Z DTEND:20211209T160000Z DTSTAMP:20240329T082742Z UID:6891de17-671e-448d-b3ad-c652351225e6 SEQUENCE:2 CREATED:20211207T152047Z DESCRIPTION:(Contactar Ana Bela Cardoso para password)ana.bela.cardoso@tec nico.ulisboa.pt LAST-MODIFIED:20211207T153317Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/classical-and-quantum-simulat ion-of-extreme-plasma-physics/ X-ALT-DESC;FMTTYPE=text/html:(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecnico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:Observers in black hole spacetimes: The inside story DTSTART:20211209T143000Z DTEND:20211209T163000Z DTSTAMP:20240329T082742Z UID:763e3ab8-cbbf-48e6-8e3e-22ed2a9b052e SEQUENCE:2 CREATED:20211207T101850Z DESCRIPTION:We consider several different aspects connected with propertie s of the motion of observers and particles inside the event horizon of a S chwarzschild black hole. We elucidate (i) how to maximize the observer 7\;s survival proper time and (ii) how to make the visible part of the out er universe as large as possible before the observer hits the singularity. We also consider the red and blueshifts of photons experienced by observe rs during their travel. We develop an approach that relates these properti es with the formalism of particle collisions in a black hole spacetime and we show that for a special class of observers\, the ones with zero moment um\, there exists an analogue of the Banados-Silk-West effect inside the h orizon. LAST-MODIFIED:20211207T162246Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/observers-in-black-hole-space times-the-inside-story/ X-ALT-DESC;FMTTYPE=text/html:We consider several different aspects connected with properties of the motion of observers an d particles inside the event horizon of a Schwarzschild black hole. We elu cidate (i) how to maximize the observer'\;s survival proper time and ( ii) how to make the visible part of the outer universe as large as possibl e before the observer hits the singularity. We also consider the red and b lueshifts of photons experienced by observers during their travel. We deve lop an approach that relates these properties with the formalism of partic le collisions in a black hole spacetime and we show that for a special cla ss of observers\, the ones with zero momentum\, there exists an analogue o f the Banados-Silk-West effect inside the horizon.
END:VEVENT BEGIN:VEVENT SUMMARY:Use of MHD Activity for Disruption Prediction in Tokamaks DTSTART:20211209T170000Z DTEND:20211209T190000Z DTSTAMP:20240329T082742Z UID:de072ea0-b440-4951-9b86-3f338fa25aa8 SEQUENCE:2 CREATED:20211207T152152Z DESCRIPTION: LAST-MODIFIED:20211207T153125Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/use-of-mhd-activity-for-disru ption-prediction-in-tokamaks/ END:VEVENT BEGIN:VEVENT SUMMARY:Dynamical bosonic stars and gravitational waves DTSTART:20211215T110000Z DTEND:20211215T130000Z DTSTAMP:20240329T082742Z UID:c6f08f71-df83-4368-9760-ff219e53509d SEQUENCE:1 CREATED:20211210T145823Z DESCRIPTION: Bosonic stars are theoretical exotic compact objects made of ultralight bosonic particles that could explain part of dark matter. In th is talk\, I will review some recent results on the stability and dynamical formation of these objects. Then I will talk about bosonic star mergers\, the emission of gravitational waves\, and what we could learn about them from a real gravitational wave event\, if these stars exist in the Univers e. LAST-MODIFIED:20211210T145823Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/dynamical-bosonic-stars-and-g ravitational-waves/ X-ALT-DESC;FMTTYPE=text/html:Bosonic stars are theoretical exotic compact objects made of ultralight bosonic particles th at could explain part of dark matter. In this talk\, I will review some re cent results on the stability and dynamical formation of these objects. Th en I will talk about bosonic star mergers\, the emission of gravitational waves\, and what we could learn about them from a real gravitational wave event\, if these stars exist in the Universe.
END:VEVENT BEGIN:VEVENT SUMMARY:Evolution of the impact of oil prices on electricity\, natural gas \, and coal prices: causality and interaction DTSTART:20211215T143000Z DTEND:20211215T163000Z DTSTAMP:20240329T082742Z UID:b821cb87-ed0a-4a0b-bf5d-344da17d3f2e SEQUENCE:1 CREATED:20211213T164048Z DESCRIPTION: (Contactar Ana Bela Cardoso para password)ana.bela.cardoso@te cnico.ulisboa.pt LAST-MODIFIED:20211213T164048Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/evolution-of-the-impact-of-oi l-prices-on-electricity-natural-gas-and-coal-prices-causality-and-interact ion/ X-ALT-DESC;FMTTYPE=text/html:
(Contactar Ana Bela Cardoso para password)
ana.bela.cardoso@tecnico.ulisboa.pt
END:VEVENT BEGIN:VEVENT SUMMARY:Using atom-like spins in semiconductors toward scalable quantum co mputing DTSTART:20211215T160000Z DTEND:20211215T180000Z DTSTAMP:20240329T082742Z UID:ab1081bb-6338-4e18-bf66-c732583163de SEQUENCE:11 CREATED:20211206T100451Z DESCRIPTION:Password: 921026In a world where the amount of data to process is steadily increasing\, the quantum nature of matter offers new possibil ities to develop concepts\, which may overcome nowadays technologies. Imp lications are expected in research areas that can range from quantum comp utation\, cryptography\, and quantum simulation.To be useful\, a qubit (th e elementary quantum unit of information) needs to be both isolated from i ts environment and precisely controllable\, which places strict requireme nts on its physical realization. In particular\, spins in solids are one o f the most promising realizations due to their potential for scalability and miniaturization. Furthermore\, in these systems\, quantum control has been established and electron spin coherence times now exceed several sec onds. Even so\, a critical challenge in these systems consists of developi ng a robust two-qubit gate that can be scaled up to a larger network.In t his seminar\, I will overview some of the challenges of this field and int roduce a new mechanism for "\;long-range"\; interaction. Making us e of independent readout of two electron spins\, we demonstrate coherent exchange interaction mediated by a multielectron quantum dot. This result provides a possible route to the realization of multi-qubit quantum circu its based on single spins.Short bio: My research activities have mostly ce ntred on the physics of nano-devices\, and\, in particular\, on giving a d irect and "\;local"\; understanding to a significant number of fu ndamental phenomena through experiments dealing with electron quantum int erference and correlations\, Coulomb blockade\, and the quantum Hall regim e. After 2015\, my work has focused on implementing "\;spin qubits&qu ot\;\, i.e. units of quantum information represented by isolated spins con fined in solid-state systems. In the course of my career\, I have carried out research in laboratories worldwide including France\, Belgium\, Denma rk\, Australia\, and Austria. In December 2020\, I have joined the Quantu m Information Team at the Hitachi Cambridge Laboratory (UK). LAST-MODIFIED:20211207T115401Z LOCATION:(Online): https://videoconf-colibri.zoom.us/j/83876336173?pwd=eXd CV09VcjRlNEk3WTJPaE55NHJyUT09 URL:http://df.vps.tecnico.ulisboa.pt/eventos/using-atom-like-spins-in-semi conductors-toward-scalable-quantum-computing/ X-ALT-DESC;FMTTYPE=text/html:Password: 92 1026
In a
world where the amount of data to process is steadily increasing\, the qua
ntum nature of matter offers new possibilities to develop concepts\, whic
h may overcome nowadays technologies. Implications are expected in researc
h areas that can range from quantum computation\, cryptography\, and quan
tum simulation.
To be useful\, a qubit (the elementary quantum un
it of information) needs to be both isolated from its environment and prec
isely controllable\, which places strict requirements on its physical rea
lization. In particular\, spins in solids are one of the most promising re
alizations due to their potential for scalability and miniaturization. Fu
rthermore\, in these systems\, quantum control has been established and el
ectron spin coherence times now exceed several seconds. Even so\, a criti
cal challenge in these systems consists of developing a robust two-qubit g
ate that can be scaled up to a larger network.
In this seminar\,
I will overview some of the challenges of this field and introduce a new
mechanism for "\;long-range"\; interaction. Making use of indepen
dent readout of two electron spins\, we demonstrate coherent exchange inte
raction mediated by a multielectron quantum dot. This result provides a p
ossible route to the realization of multi-qubit quantum circuits based on
single spins.
< br/>
Short bio: My research activities have mostly centred on the physics of nano-devices\, and\, in particular\ , on giving a direct and "\;local"\; understanding to a significa nt number of fundamental phenomena through experiments dealing with electr on quantum interference and correlations\, Coulomb blockade\, and the qua ntum Hall regime. After 2015\, my work has focused on implementing "\ ;spin qubits"\;\, i.e. units of quantum information represented by iso lated spins confined in solid-state systems. In the course of my career\, I have carried out research in laboratories worldwide including France\, Belgium\, Denmark\, Australia\, and Austria. In December 2020\, I have jo ined the Quantum Information Team at the Hitachi Cambridge Laboratory (UK ).
END:VEVENT BEGIN:VEVENT SUMMARY:Quantum algorithm for the classification of Supersymmetric top qua rk events DTSTART:20211215T163000Z DTEND:20211215T180000Z DTSTAMP:20240329T082742Z UID:7a74c466-f3a1-48b9-8d29-187d5f7f8465 SEQUENCE:1 CREATED:20211213T143602Z DESCRIPTION: The search for supersymmetric particles is one of the major g oals in the next high luminosity phase of the Large Hadron Collider. Super symmmetric top (stop) searches play a very important role in this respect\ , but the unprecedented collision rate that will be attained at this phase poses new challenges for the separation between any new signal and the St andard Model background. While classical multivariate techniques might be insufficient in this new environment\, the massive parallelism provided by quantum computing techniques may yield an efficient solution for the prob lem. In this paper we make a novel application of the QAML-Z approach to c lassify the stop signal versus the background\, and implement it in a quan tum annealer machine. We show that this approach together with the pre-pro cessing of the data with Principal Component Analysis may yield better res ults than conventional multivariate approaches LAST-MODIFIED:20211213T143602Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/quantum-algorithm-for-the-cla ssification-of-supersymmetric-top-quark-events/ X-ALT-DESC;FMTTYPE=text/html:The search for sup ersymmetric particles is one of the major goals in the next high luminosit y phase of the Large Hadron Collider. Supersymmmetric top (stop) searches play a very important role in this respect\, but the unprecedented collisi on rate that will be attained at this phase poses new challenges for the s eparation between any new signal and the Standard Model background. While classical multivariate techniques might be insufficient in this new enviro nment\, the massive parallelism provided by quantum computing techniques m ay yield an efficient solution for the problem. In this paper we make a no vel application of the QAML-Z approach to classify the stop signal versus the background\, and implement it in a quantum annealer machine. We show t hat this approach together with the pre-processing of the data with Princi pal Component Analysis may yield better results than conventional multivar iate approaches
END:VEVENT BEGIN:VEVENT SUMMARY:Prescription for finite oblique parameters S and U in extensions o f the SM with mW != mZ cos thetaW DTSTART:20211216T110000Z DTEND:20211216T130000Z DTSTAMP:20240329T082742Z UID:c846416a-b419-4149-ac89-362a294ee9c4 SEQUENCE:3 CREATED:20211213T100710Z DESCRIPTION:Meeting ID: 849 8854 1912Meeting password: CFTP777We consider extensions of the Standard Model with neutral scalars in multiplets of SU( 2) larger than doublets. When those scalars acquire vacuum expectation val ues\, the resulting masses of the gauge bosons W± and Z0 are not related by mW = mZ cos thetaW. In those extensions of the Standard Model the obliq ue parameters S and U\, when computed at the one-loop level\, turn out to be either gauge-dependent or divergent. We show that one may eliminate thi s problem by modifying the Feynman rules of the Standard Model for some ve rtices containing the Higgs boson\; the modifying factors are equal to 1 i n the limit mW = mZ cos thetaW. We give the result for S in a model with a rbitrary numbers of scalar SU(2) triplets with weak hypercharges either 0 or 1. LAST-MODIFIED:20211213T100858Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/prescription-for-finite-obliq ue-parameters-s-and-u-in-extensions-of-the-sm-with-mw-mz-cos-thetaw/ X-ALT-DESC;FMTTYPE=text/html:Meeting ID: 849 885
4 1912
Meeting password: CFTP777
We consider extensions of the Standard Model with neutral scalars in mul tiplets of SU(2) larger than doublets. When those scalars acquire vacuum e xpectation values\, the resulting masses of the gauge bosons W± and Z0 ar e not related by mW = mZ cos thetaW. In those extensions of the Standard M odel the oblique parameters S and U\, when computed at the one-loop level\ , turn out to be either gauge-dependent or divergent. We show that one may eliminate this problem by modifying the Feynman rules of the Standard Mod el for some vertices containing the Higgs boson\; the modifying factors ar e equal to 1 in the limit mW = mZ cos thetaW. We give the result for S in a model with arbitrary numbers of scalar SU(2) triplets with weak hypercha rges either 0 or 1.
END:VEVENT BEGIN:VEVENT SUMMARY:Inference with core-collapse supernova waveforms DTSTART:20211216T143000Z DTEND:20211216T160000Z DTSTAMP:20240329T082742Z UID:1d9d3966-a309-4f10-9289-f636a0de3cf8 SEQUENCE:2 CREATED:20211210T145644Z DESCRIPTION:Parameter estimation of core-collapse supernovae (CCSN) is cha llenged by the unmodeled nature of postbounce gravitational waveforms and by the intrinsic difficulties involved in the modeling of explosions of ma ssive stars. Asteroseismology of proto-neutron stars (PNS) may offer a pro mising approach to do so. Numerical simulations of CCSN show that g-modes are commonly excited in PNS and they are responsible for a significant fra ction of the gravitational-wave signal produced by most (i.e. neutrino-dri ven) supernova explosions. The time-frequency evolution of those modes is linked to the physical properties of the PNS through quasi-universal relat ions. This talk discusses recent work aimed at inferring PNS properties th rough the analysis of its modes of oscillation and the gravitational waves they trigger. Observational constraints of our findings for current and t hird-generation gravitational-wave detectors are reported. In the last par t of the talk we will also cover recent results for the rather specific ca se of rapidly-rotating CCSN. LAST-MODIFIED:20211216T085805Z LOCATION:Sala de Formação Avançada\, 2-8.11\, Pavilhão de Física\, 2 º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/inference-with-core-collapse- supernova-waveforms/ X-ALT-DESC;FMTTYPE=text/html:Parameter estimatio n of core-collapse supernovae (CCSN) is challenged by the unmodeled nature of postbounce gravitational waveforms and by the intrinsic difficulties i nvolved in the modeling of explosions of massive stars. Asteroseismology o f proto-neutron stars (PNS) may offer a promising approach to do so. Numer ical simulations of CCSN show that g-modes are commonly excited in PNS and they are responsible for a significant fraction of the gravitational-wave signal produced by most (i.e. neutrino-driven) supernova explosions. The time-frequency evolution of those modes is linked to the physical properti es of the PNS through quasi-universal relations. This talk discusses recen t work aimed at inferring PNS properties through the analysis of its modes of oscillation and the gravitational waves they trigger. Observational co nstraints of our findings for current and third-generation gravitational-w ave detectors are reported. In the last part of the talk we will also cove r recent results for the rather specific case of rapidly-rotating CCSN.
END:VEVENT BEGIN:VEVENT SUMMARY:Quantum Link Prediction in Complex Networks DTSTART:20211217T090000Z DTEND:20211217T110000Z DTSTAMP:20240329T082742Z UID:0c2ad62e-a81c-480e-9439-ac336984aeae SEQUENCE:7 CREATED:20211213T155130Z DESCRIPTION:Password: 392699Meeting ID: 836 1514 8258Predicting new l inks in physical\, biological\, social\, or technological networks has a s ignificant scientific and societal impact. Network based link prediction m ethods utilize topological patterns in a network to infer new or unobserve d links. Here\, we propose a quantum algorithm for link prediction\, QLP\, which uses quantum walks to infer unknown links based on even and odd len gth paths. By sampling new links from quantum measurements\, QLP avoids th e need to explicitly calculate all pairwise scores in the network. We stud y the complexity of QLP and discuss in which cases one may achieve a polyn omial speedup over classical link prediction methods. Furthermore\, tests with real-world datasets show that QLP is at least as precise as state-of- the-art classical link prediction methods\, both in cross-validation tests and in the prediction of experimentally verified protein-protein interact ions. LAST-MODIFIED:20211213T164438Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/quantum-link-prediction-in-co mplex-networks/ X-ALT-DESC;FMTTYPE=text/html:Password: 392699
Meeting ID: 836 1514 8258
Predicting new links in physical\, biological\, social\,
or technological networks has a significant scientific and societal impac
t. Network based link prediction methods utilize topological patterns in a
network to infer new or unobserved links. Here\, we propose a quantum alg
orithm for link prediction\, QLP\, which uses quantum walks to infer unkno
wn links based on even and odd length paths. By sampling new links from qu
antum measurements\, QLP avoids the need to explicitly calculate all pairw
ise scores in the network. We study the complexity of QLP and discuss in w
hich cases one may achieve a polynomial speedup over classical link predic
tion methods. Furthermore\, tests with real-world datasets show that QLP i
s at least as precise as state-of-the-art classical link prediction method
s\, both in cross-validation tests and in the prediction of experimentally
verified protein-protein interactions.
O Departamento de F ísica celebrou 40 anos em 2020\, mas está maior e mais dinâmico que nun ca. Nesta cerimónia anual vamos rever e celebrar o ano corrente\, homenag eando membros e alunos do DF. A fechar\, haverá um momento musical com o pianista Filipe Pinto-Ribeiro.
END:VEVENT BEGIN:VEVENT SUMMARY:Novel architectures to integrate ultra sensitive sensors to detect biomedical signals DTSTART:20220111T143000Z DTEND:20220111T163000Z DTSTAMP:20240329T082742Z UID:50b83ca3-48bc-47eb-86e0-4ae78a78d7b6 SEQUENCE:2 CREATED:20220107T180846Z DESCRIPTION:Magnetic sensing technologies are widely used in biomedical ap plications wherein magnetoresistive sensors are stated due to a high perfo rmance in terms of signal-to-noise ratio\, power consumption and productio n cost. Furthermore\, they work at room temperature with an established nT esla minimum field detectable at low frequencies. However\, an improvement on the limit field detection can push forward the magnetoresistive techno logy as a high precision tool within the sub-nT field range. The key param eters of the magnetoresistive sensor performance are given by sensitivity\ , noise\, power consumption\, thermal and magnetic robustness. A proper mu ltilayer stack engineering focused on materials and thicknesses of the buf fer layer (Ta\, NiFeCr)\, antiferromagnetic material (MnNi\, MnIr)\, refer ence structure (exchange bias\, synthetic antiferromagnet) and sensing lay er can deliver an enhanced response according to the application requireme nts. Instead of a sensitivity enhancement driven by a higher MR ratio\, th e incorporation of magnetic flux concentrators provides a reduction of the linear range. However\, the operational point of the latter approach is u sually deviated from zero field due to its high sensitivity and hysteresis \, being explored a monolithic biasing technique to compensate the shift o f the output curve through the integration a current line directly on chip . On the other hand\, the optimization of the minimum field detectable can also be delivered by a noise level reduction. Therefore\, a vertical depo sition of Z spin valve levels was assessed in order to achieve a compact p arallel configuration with an equivalent resistance reduced by a factor of 1/Z. This work comprised the optimization of the deposition and microfabr ication process for a thick multilayer stack\; development of simulation a nd calculation tools to understand the physics behind and to support the d evice design\; magnetic\, magnetotransport and noise characterization of t he microfabricated devices\, and implementation of an experimental set-up to find the minimum field detectable within an unshielded environment. Pac ked devices composed of up to 50 spin valves vertically deposited and larg e sensing areas (low aspect ratio) led to a low nominal resistance combine d with a linear and centered output driven by all magnetostatic couplings between ferromagnetic layers. This approach minimizes the noise level whil e maintaining a high sensitivity delivering an improved detectivity withou t compromising the device footprint. A 3D architecture design integrating magnetic tunnel junctions was pursued to push forward the detectivity of t unnel magnetoresistive sensors. The concept was demonstrated with a CoFeB/ MgO/CoFeB based stack\, being established a microfabrication process for a device composed of 3 levels. The characterized device presents a low nois e level in addition to a high electrical robustness and compact footprint. LAST-MODIFIED:20220107T181312Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/novel-architectures-to-integr ate-ultra-sensitive-sensors-to-detect-biomedical-signals/ X-ALT-DESC;FMTTYPE=text/html:Magnetic sensing te
chnologies are widely used in biomedical applications wherein magnetoresis
tive sensors are stated due to a high performance in terms of signal-to-no
ise ratio\, power consumption and production cost. Furthermore\, they work
at room temperature with an established nTesla minimum field detectable a
t low frequencies. However\, an improvement on the limit field detection c
an push forward the magnetoresistive technology as a high precision tool w
ithin the sub-nT field range.
The key parameters of the magnetor
esistive sensor performance are given by sensitivity\, noise\, power consu
mption\, thermal and magnetic robustness. A proper multilayer stack engine
ering focused on materials and thicknesses of the buffer layer (Ta\, NiFeC
r)\, antiferromagnetic material (MnNi\, MnIr)\, reference structure (excha
nge bias\, synthetic antiferromagnet) and sensing layer can deliver an enh
anced response according to the application requirements.
Instea
d of a sensitivity enhancement driven by a higher MR ratio\, the incorpora
tion of magnetic flux concentrators provides a reduction of the linear ran
ge. However\, the operational point of the latter approach is usually devi
ated from zero field due to its high sensitivity and hysteresis\, being ex
plored a monolithic biasing technique to compensate the shift of the outpu
t curve through the integration a current line directly on chip. On the ot
her hand\, the optimization of the minimum field detectable can also be de
livered by a noise level reduction.
Therefore\, a vertical depos
ition of Z spin valve levels was assessed in order to achieve a compact pa
rallel configuration with an equivalent resistance reduced by a factor of
1/Z. This work comprised the optimization of the deposition and microfabri
cation process for a thick multilayer stack\; development of simulation an
d calculation tools to understand the physics behind and to support the de
vice design\; magnetic\, magnetotransport and noise characterization of th
e microfabricated devices\, and implementation of an experimental set-up t
o find the minimum field detectable within an unshielded environment. Pack
ed devices composed of up to 50 spin valves vertically deposited and large
sensing areas (low aspect ratio) led to a low nominal resistance combined
with a linear and centered output driven by all magnetostatic couplings b
etween ferromagnetic layers. This approach minimizes the noise level while
maintaining a high sensitivity delivering an improved detectivity without
compromising the device footprint. A 3D architecture design integrating m
agnetic tunnel junctions was pursued to push forward the detectivity of tu
nnel magnetoresistive sensors.
The concept was demonstrated with
a CoFeB/MgO/CoFeB based stack\, being established a microfabrication proc
ess for a device composed of 3 levels. The characterized device presents a
low noise level in addition to a high electrical robustness and compact f
ootprint.
Optical resonators allow the gene
ration and storage of electromagnetic waves. They are widely used in techn
ology and fundamental research\, notably for their application in telecomm
unications\, lasers and nonlinear optics\, ultra-sensitive measurements in
cavity optomechanics and the study of light-matter interactions. To some
extent\, it is possible to create structured light\, i.e.\, to customize i
t by controlling its amplitude\, phase\, frequency\, and polarization\, di
rectly inside a resonator\, but the typical approaches used since the inve
ntion of the laser\, such as pump shaping and designing different cavity g
eometries\, are macroscopic and rather limited. In my most recent research
\, I have explored new cavity configurations incorporating metamaterials w
ith structured elements smaller than the wavelength of light\, allowing li
ght to be shaped in unprecedented ways. These demonstrations range from em
bedding a mode converter inside a solid-state resonator to create tunable
optical vortex arrays\, to the use of mode converters as one or both cavit
y reflectors in external cavity lasers and silicon-on-insulator waveguides
to enable lasing on holograms and create arbitrary near fields\, to the m
onolithic integration into semiconductor lasers to engineer the spectrum o
f optical frequency combs. In all these cases\, internal mode conversion c
onfers intriguing new properties to these metaresonators\, which cannot be
derived from the properties of the base materials constituting the gain o
r waveguide medium\, nor from the cavity geometry. In this seminar\, I wil
l provide an overview of this emerging field combining resonators with cus
tomized intracavity optical elements\, which is one of the most complex an
d richest frontiers in optics.
Bio: Marco Piccardo is a Re
searcher at the Istituto Italiano di Tecnologia in Milan leading a small t
eam within the Vectorial Nano-Imaging research line. He is exploring novel
approaches for structured light based on metasurfaces and their integrati
on in active laser resonators. He is also an Associate Researcher at Harva
rd University\, where he did his postdoctoral studies from 2016 to 2020 ex
ploring new electronic and photonic properties of integrated laser frequen
cy combs. He obtained his Ph.D. in Physics in 2016 from Ecole Polytechniqu
e working on the fundamental electronic processes responsible for the effi
ciency drop of blue light-emitting diodes at high-current operation\, such
as Anderson localization and Auger recombination. He received his B.Sc. i
n Physics from Università degli Studi di Torino\, and a M.Sc. in Physics
from Ecole Normale Superieure and Ecole Polytechnique.
Abstract:
The new technical paradigm of Industry 4.0 has been pushing the sensor
technology\, instrumentation\, and measurement science to continue the pro
gression of achieving the control and efficiency over the entire mass prod
uction process. Therefore\, the development of smart and autonomous system
s has led to a high demand of sensors for the monitorization of angular an
d linear positioning among the industrial\, automotive and robotics market
.
The main limitations of the existing m
agnetic sensing technology based on state-of-art anisotropic magnetoresist
ive and hall effect sensors for incremental and absolute positioning syste
ms rely on a low reading distance and a minimum pole pitch size down to 50
0 µm\, which leads to a lower resolution and accuracy when compared to op
tical based encoders.
The recent developments on magnetoresistiv
e sensor technologies provide a competitive and reliable solution for the
next generation of motion systems based on magnetic encoders\, where the h
igh signal-to-noise ratio and the enhanced spatial resolution of tunnel ma
gnetoresistive sensors (TMR) can promote the detection of sub-100 µm pole
pitch dimensions\, driving to a performance similar to low-level optical
encoders in terms of accuracy but with a lower production cost\, enhanced
working distance\, reduced mounting tolerances and higher robustness to ha
rsh environments.
Therefore\, following the technological trend
observed in the hard disk devices\, the development of the new generation
of incremental magnetic encoders based on the TMR sensing technology focus
ed on the (i) enhancement of the device reading distance beyond a gap equi
valent to 1x pole pitch dimension and on the (ii) improvement of the accur
acy employing (a) commercial elastomer bonded ferrite linear scales from a
sub-100µm to a 5 mm pole pitch range and (b) microfabricated thin film m
agnetic scales based on a pole-groove pattern with a sub-500 µm pole pitc
h range.
The optimization of the sensing
technology\, the sensor arrangement and packaging method delivered a succ
essful outcome for a future short-term breakthrough on the available encod
er solutions by achieving an accuracy around 3 µm at a reading distance o
f 1x for a pole pitch of 80 µm. On the other hand\, a reading distance ra
nge around 3x was achieved for standard pole pitch dimensions\, being able
to reduce the mounting requirements in non-accurate applications.
Abstract:
Quantum materials exhibit a variety of dif
ferent phases that arise from the competition between different degrees of
freedom – electronic\, structural\, spin and orbital. Ultrafast tec
hniques enable a selective investigation of the dynamical response of thes
e different subsystems through a careful choice of pump and probe characte
ristics.
I will present results of
studies in different quantum materials using ultrafast pulses in the optic
al\, THz and x-ray frequency ranges.
TbMnO3 is a prototypical multiferroic\, where ferroelectric polarization
arises from a cycloidal magnetic order below 27 K. The prospect of electr
ic field control of magnetization dynamics makes multiferroic systems extr
emely appealing\, in particular in the context of ultrafast magnetic switc
hing. Using ultrafast x-ray pulses we have investigated the magnetic order
and structural dynamics in TbMnO_3 following optical and THz excitation\,
shedding light onto the demagnetization pathways in this system.
Mott insulators are archetypal examples of
quantum materials\, which have generated strong interest due in part to th
e insulator-to-metal transition that some exhibit when the balance between
on-site Coulomb repulsion and hopping is overturned. Some Mott insulators
exhibit an abrupt drop in resistivity under the application of electric f
ields with durations of a few tens of microseconds\, with typical threshol
d fields on the order of 1-10 kV/cm. Quasi-dc electric fields well in exce
ss of 1 – 10 kV/cm can currently be generated with ultrashort pulses in
the low frequency or THz range\, which enables the investigation of the su
b-picosecond dynamics of the electric field driven Mott transition. I will
present our results on THz driven dynamics in GaTa_4Se_8\, a Mott insulat
or which exhibits clear electrical Mott transitions.
Short Bio:
Elsa Abreu is a Senior Research As
sistant in the Physics Department of ETH Zürich. In 2018 she was awarded
a four-year Ambizione Grant from the Swiss National Science Foundation for
her project on "\;Exploring superconductivity pathways in low-dimensi
onal spin-ladder and spin-chain compounds"\;\, and has since then been
leading a team as a part of the Ultrafast Dynamics Group.
She obtained her BSc in Physics from the Instituto Superior Técnico and her MSc at Instituto Superior Técnico and Uppsala University\, Sweden. In 2014 she graduated with her PhD in Physics from Bo ston University\, MA\, USA\, and then moved to Switzerland to work as a po stdoctoral fellow at ETH Zürich.
END:VEVENT BEGIN:VEVENT SUMMARY:Assessment of reflectometry diagnostics for DEMO DTSTART:20220126T090000Z DTEND:20220126T110000Z DTSTAMP:20240329T082742Z UID:2f55a025-69c4-4dc0-9a91-8476ef652ed6 SEQUENCE:4 CREATED:20220111T145319Z DESCRIPTION:Abstract: DEMO will be the first prototype of a fusion power p lant. Unlike experimental tokamaks\, only the necessary diagnostics for ma chine protection and plasma control will be implemented. One of the fundam ental measurements is the position and shape of the last closed magnetic s urface\, typically measured with the magnetic diagnostics. One of the majo r issues of its implementation in DEMO is the large integration drifts tha t can occur during the operation due to the high levels of radiation. This can lead to a wrong plasma position estimation\, putting the operation at risk.The prime candidate to complement or substitute the magnetic diagnos tics in DEMO is the microwave reflectometry. By sweeping the frequency of the probing beam\, microwave reflectometry is capable of measuring the ele ctron density profile. As the density is directly linked to the magnetic f lux surfaces these measurements give access to the magnetic configuration\ , providing its local radial position. The O-mode propagation is independe nt from the magnetic field\, being ideal for replacing the magnetic diagno stics.The DEMO plasma position reflectometer (DEMO PPR) consists a system of multi reflectometers distributed poloidaly along the wall at differen t positions that will provide the separatrix reconstruction. The optimizat ion of such system requires the simulation of the measurement process for different poloidal views\, emitting angles\, antenna assemblies and plasma configurations. The final system must be optimized for the operation scen ario and be stable under the possible deviations to its equilibrium that c an occur during the discharges. This includes the plasma displacement\, tu rbulence or MHD activity. For now\, the DEMO PPR is in an early developmen t stage and there are many questions that need to be investigated before r eaching its final design.In this work we study the process of optimization of PPR systems with a general approach\, taking into account the future c hanges in the geometry and plasma scenario. The important variables of a g eneral multiple reflectometers system were identified and the techniques a nd the procedure to optimize it were developed. The simulation of such sys tems is in general a complex task that requires the definition of several different regions of interest and testing different antenna models and pla smas\, which is a very demanding task from the computational point of view and of necessary time to build the simulation scripts. For this reason\, we develop the structure of a high-level framework for multiple reflectome try simulations that is capable of automatizing all the simulation process of a multiple reflectometers system for the REFMUL* codes\, a family of f ull wave FDTD codes that has been used for reflectometry simulations. Th e user defines the configuration files of the system geometry and plasma\, the probing bands and the dependence between the main variables of the pr oblem. A script creates all the necessary models and scripts that to run a ll the simulations in the HPCs.Using the developed framework\, we optimize d the DEMO PPR system using the official DEMO scenario from EUROFUSION. We started by defining 100 different positions around the tokamak and testin g two different configurations. In the first one\, the antennas were align ed perpendicularly with the wall. This configuration has advantages from t he point of view of the implementation of the antennas. However\, the resu lts shown that there are positions in the top of the machine and in the di vertor region that have a very poor measurement performance and in some ca ses the signal is totally lost. In the second configuration\, the antennas were aligned perpendicularly to the separatrix. In this case\, since the direction of the probing beam is approximately parallel to the density gra dient\, a better measurement performance is expected. The results confirme d this principle\, improving the results in several positions. At the dive rtor region\, some of the positions continued to have a poor measurement p erformance\, being necessary to sweep the probing angle to verify if there is an optimized configuration.One of the problems associated with the opt imization is that is necessary to extract the round trip group delay and c alculate the amplitude of the detected signal for many different configura tions. The analysis of the simulation results requires the manual adjustme nt of the data analysis parameters\, as the filter cutoff frequency or the signal delay. Using the principle that a slow varying group delay has a m inimum standard deviation if it is well filtered\, we developed an automat ized version of the the 1/Q detection\, designed as IQA method. With this technique\, it was possible sweeping the probing angle at all the position s in an acceptable time and select the optimized configuration. The maximu m average detected amplitude shown to be a good selection criteria for the optimized configuration. The results show that\, with the exception of so me positions in the divertor region\, there is an optimized configuration with low position error {<\;1 cm) and the power losses minimized.With th e optimized configuration\, the stability of the system was tested for pla sma displacements of 5 (reference case) and 15 cm (limit case). The result s show that\, in contrast to the results of the configuration with the ant ennas perpendicular to the separatrix\, the system is stable for 5 cm plas ma displacements in different directions (0\, 90\, 180 and 270 degrees). F or displacements of 15 cm\, the positions at the top of the machine can re ach errors in the order of the minimum error requirement (1 cm).The effect of turbulence in reflectometry measurements was studied in one gap of the equatorial region\, in the high field side. Due to the lack of informatio n on the turbulence properties of DEMO plasmas\, the fluctuations were def ined with an analytical model. A Kolmogorov-like spectrum was used to gene rate 400 random plasma samples for 16 different levels of amplitude (1-16% )\, compatible with the order of values observed in the experiments. Using the IQA algorithm\, the principal statistical parameters were calculated. The results show that for higher levels of turbulence ($>\;5%$)\, the m ean position error becomes negative due to the change of the effective cut off position. This effect occurs for all the frequencies\, leading to an a ccumulative error that can affect the position measurement in the order of accuracy requirements. In order to prove the reliability of the entire sy stem\, it is necessary to apply the same procedure to the other positions of the system\, which requires a huge amount of computation time on HPCs t o be done.The techniques and the algorithms developed in this work can be applied in other processes which involve the analysis of a high number of reflectometry simulations\, including studies with other reflectometry tec hniques. LAST-MODIFIED:20220118T093813Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/assessment-of-reflectometry-d iagnostics-for-demo/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
DEMO will be the first prototype of a fus
ion power plant. Unlike experimental tokamaks\, only the necessary diagnos
tics for machine protection and plasma control will be implemented. One of
the fundamental measurements is the position and shape of the last closed
magnetic surface\, typically measured with the magnetic diagnostics. One
of the major issues of its implementation in DEMO is the large integration
drifts that can occur during the operation due to the high levels of radi
ation. This can lead to a wrong plasma position estimation\, putting the o
peration at risk.
The prime candida
te to complement or substitute the magnetic diagnostics in DEMO is the mic
rowave reflectometry. By sweeping the frequency of the probing beam\, micr
owave reflectometry is capable of measuring the electron density profile.
As the density is directly linked to the magnetic flux surfaces these meas
urements give access to the magnetic configuration\, providing its local r
adial position. The O-mode propagation is independent from the magnetic fi
eld\, being ideal for replacing the magnetic diagnostics.
The DEMO plasma position reflectometer (DEMO PPR) c
onsists a system of multi reflectometers distributed poloidaly along the
wall at different positions that will provide the separatrix reconstructi
on. The optimization of such system requires the simulation of the measure
ment process for different poloidal views\, emitting angles\, antenna asse
mblies and plasma configurations. The final system must be optimized for t
he operation scenario and be stable under the possible deviations to its e
quilibrium that can occur during the discharges. This includes the plasma
displacement\, turbulence or MHD activity. For now\, the DEMO PPR is in an
early development stage and there are many questions that need to be inve
stigated before reaching its final design.
In this work we study the process of optimization of PPR systems w
ith a general approach\, taking into account the future changes in the geo
metry and plasma scenario. The important variables of a general multiple r
eflectometers system were identified and the techniques and the procedure
to optimize it were developed. The simulation of such systems is in genera
l a complex task that requires the definition of several different regions
of interest and testing different antenna models and plasmas\, which is a
very demanding task from the computational point of view and of necessary
time to build the simulation scripts. For this reason\, we develop the st
ructure of a high-level framework for multiple reflectometry simulations t
hat is capable of automatizing all the simulation process of a multiple re
flectometers system for the REFMUL* codes\, a family of full wave FDTD c
odes that has been used for reflectometry simulations. The user defines th
e configuration files of the system geometry and plasma\, the probing band
s and the dependence between the main variables of the problem. A script c
reates all the necessary models and scripts that to run all the simulation
s in the HPCs.
Using the developed
framework\, we optimized the DEMO PPR system using the official DEMO scena
rio from EUROFUSION. We started by defining 100 different positions around
the tokamak and testing two different configurations. In the first one\,
the antennas were aligned perpendicularly with the wall. This configuratio
n has advantages from the point of view of the implementation of the anten
nas. However\, the results shown that there are positions in the top of th
e machine and in the divertor region that have a very poor measurement per
formance and in some cases the signal is totally lost. In the second confi
guration\, the antennas were aligned perpendicularly to the separatrix. In
this case\, since the direction of the probing beam is approximately para
llel to the density gradient\, a better measurement performance is expecte
d. The results confirmed this principle\, improving the results in several
positions. At the divertor region\, some of the positions continued to ha
ve a poor measurement performance\, being necessary to sweep the probing a
ngle to verify if there is an optimized configuration.
One of the problems associated with the optimization i
s that is necessary to extract the round trip group delay and calculate th
e amplitude of the detected signal for many different configurations. The
analysis of the simulation results requires the manual adjustment of the d
ata analysis parameters\, as the filter cutoff frequency or the signal del
ay. Using the principle that a slow varying group delay has a minimum stan
dard deviation if it is well filtered\, we developed an automatized versio
n of the the 1/Q detection\, designed as IQA method. With this technique\,
it was possible sweeping the probing angle at all the positions in an acc
eptable time and select the optimized configuration. The maximum average d
etected amplitude shown to be a good selection criteria for the optimized
configuration. The results show that\, with the exception of some position
s in the divertor region\, there is an optimized configuration with low po
sition error {<\;1 cm) and the power losses minimized.
With the optimized configuration\, the stability of
the system was tested for plasma displacements of 5 (reference case
) and 15 cm (limit case). The results show that\, in contrast to the resul
ts of the configuration with the antennas perpendicular to the separatrix\
, the system is stable for 5 cm plasma displacements in different d
irections (0\, 90\, 180 and 270 degrees). For displacements of 15 cm\, the
positions at the top of the machine can reach errors in the order of the
minimum error requirement (1 cm).
T
he effect of turbulence in reflectometry measurements was studied in one g
ap of the equatorial region\, in the high field side. Due to the lack of i
nformation on the turbulence properties of DEMO plasmas\, the fluctuations
were defined with an analytical model. A Kolmogorov-like spectrum was use
d to generate 400 random plasma samples for 16 different levels of amplitu
de (1-16%)\, compatible with the order of values observed in the experimen
ts. Using the IQA algorithm\, the principal statistical parameters were ca
lculated. The results show that for higher levels of turbulence ($>\;5%$
)\, the mean position error becomes negative due to the change of the effe
ctive cutoff position. This effect occurs for all the frequencies\, leadin
g to an accumulative error that can affect the position measurement in the
order of accuracy requirements. In order to prove the reliability of the
entire system\, it is necessary to apply the same procedure to the other p
ositions of the system\, which requires a huge amount of computation time
on HPCs to be done.
The techniques and the algorithms developed in this work can be applied in other processe s which involve the analysis of a high number of reflectometry simulations \, including studies with other reflectometry techniques.
END:VEVENT BEGIN:VEVENT SUMMARY:Minimal Solutions to the CKM Unitarity Problem with a Vector-like Quark Isosinglet DTSTART:20220203T120000Z DTEND:20220203T140000Z DTSTAMP:20240329T082742Z UID:d20eb2d9-83e9-468e-b28b-340679ebed57 SEQUENCE:8 CREATED:20220131T101029Z DESCRIPTION:Abstract:Cálculos e resultados recentes apresentam fortes evi dências de que a matriz CKM não é unitária\, contradizendo o MP e suge rindo a existência de Nova Física (NF). Nesta tese\, propomos uma extens ão mínima do Modelo Padrão (MP) com um quark vector-like do tipo up\, q ue fornece uma solução simples para o problema da unitaridade da matriz CKM (CKM-UP).Adotamos a parametrização Botella-Chau para a matriz de mis tura \, usando os três ângulos e fase habituais da matriz do MP\, mais t rês ângulos extra e duas novas fases. São obtidas características inte ressantes e um novo padrão de decaimentos do \, predominantemente para a primeira geração. Averiguou-se também se os limites pelos Electroweak P recision Measurements (EWPM) são excedidos. LAST-MODIFIED:20220203T210102Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/minimal-solutions-to-the-ckm- unitarity-problem-with-a-vector-like-quark-isosinglet/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
b>
Cálculos e resultados recentes apresentam
fortes evidências de que a matriz CKM não é unitária\, contradizendo
o MP e sugerindo a existência de Nova Física (NF). Nesta tese\, propomos
uma extensão mínima do Modelo Padrão (MP) com um quark vector-like<
/i> do tipo up\, que fornece uma solução simples para o problema
da unitaridade da matriz CKM (CKM-UP).
Adotamos a parametrização Botella-Chau para a matriz de mistura \, u sando os três ângulos e fase habituais da matriz do MP\, mais três âng ulos extra e duas novas fases. São obtidas características interessantes e um novo padrão de decaimentos do \, predominantemente para a primeira geração. Averiguou-se também se os limites pelos Electroweak Precisi on Measurements (EWPM) são excedidos.
END:VEVENT BEGIN:VEVENT SUMMARY:Dark matter in three-Higgs-doublet models with S3 symmetry DTSTART:20220209T161500Z DTEND:20220209T180000Z DTSTAMP:20240329T082742Z UID:aeae4cba-948f-4337-a358-d1bff207fdc4 SEQUENCE:6 CREATED:20220127T103054Z DESCRIPTION:Abstract:Models with two or more scalar doublets with discrete or global symmetries can have vacua with vanishing vacuum expectation val ues in the bases where symmetries are imposed. If a suitable symmetry stab ilises such vacua\, these models may lead to interesting dark matter candi dates\, provided that the symmetry prevents couplings among the dark matte r candidates and the fermions. We analyse three-Higgs-doublet models with an underlying S3 symmetry and discuss all possible vacua.Two models\, with and without CP violation\, are explored in detail. In our framework the s tability of the dark matter sector results from a Z2 symmetry which surviv es the spontaneous symmetry breakdown of the initial S3 symmetry. One of t he doublets provides the DM sector\, while the other two are active. LAST-MODIFIED:20220127T103407Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/dark-matter-in-three-higgs-do ublet-models-with-s3-symmetry/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
b>
Models with two or more scalar doublets wi
th discrete or global symmetries can have vacua with vanishing vacuum expe
ctation values in the bases where symmetries are imposed. If a suitable sy
mmetry stabilises such vacua\, these models may lead to interesting dark m
atter candidates\, provided that the symmetry prevents couplings among the
dark matter candidates and the fermions. We analyse three-Higgs-doublet m
odels with an underlying S3 symmetry and discuss all possible vacua.
<
br/>Two models\, with and without CP violation\, are explored in detail. I
n our framework the stability of the dark matter sector results from a Z2
symmetry which survives the spontaneous symmetry breakdown of the initial
S3 symmetry. One of the doublets provides the DM sector\, while the other
two are active.
Meeting ID: 849 885
4 1912
Meeting password: CFTP777
Abstract:
Severa
l theoretical and experimental problems require that the Standard Model of
particle physics is extended. The fact that three generations of quarks a
nd leptons exist is not understood\, but it does not belong to this list o
f problems. The fermion masses and mixings show\, however\, apparent regul
arities and hierarchies which suggest that it could be related to and unde
rstood by new physics. The talk will cover some existing ideas how the fla
vour structures might emerge and it will cover recent work which maps the
structures onto new parameters which may be easier to explain.
Abstract:
Starting from a generalization of the good-bad-ugly model\, we showed th
at the solutions to the Einstein field equations in generalized harmonic g
auge (GHG) admit polyhomogeneous expansions near null infinity. This allow
s us to find out\, under a very general class of initial data\, whether th
e peeling property holds for each gauge choice. In general\, we find that
it does not. However we find that the interplay between gauge and constrai
nt addition can be exploited in order to recover peeling. The same method
can be used to build a regularization of the Einstein field equations in G
HG.
Abstract:
Hints for the violation of lepton flavour universality (satisfied withi
n the SM) have accumulated in recent years. In particular\, deviations fro
m the SM predictions were observed in semi-leptonic B decays (b->\;sll a
nd b->\;ctau)\, in the anomalous magnetic moment of the muon (g-2)\, in
leptonic tau decays and di-electron searches. Furthermore\, also the defic
it in first row CKM unitarity\, known as the Cabibbo Angle Anomaly\, can b
e interpreted as a sign of lepton flavour universality violation. In this
talk I review the status of these anomalies and give an overview of the po
ssible interpretations in terms of new physics models.
ABSTRACT: < br/>I will present torsion bigravity\, which is a theory of dynamical mass ive spin-2 field of geometrical origin (dynamical torsion field). I will c over various issues as: - motivation and theoretical basement of this type of modified gravity\; - the torsion bigravity world: known solutions and their physical properties\, phenomenological consequences. In particular\, I will discuss some consequences for the black hole physics.
END:VEVENT BEGIN:VEVENT SUMMARY:Extreme particle acceleration in astrophysical plasmas: from simul ations to observations via laboratory experiments DTSTART:20220302T160000Z DTEND:20220302T180000Z DTSTAMP:20240329T082742Z UID:8ebe2421-6854-4958-a2be-acdf43c2acbe SEQUENCE:5 CREATED:20220103T124232Z DESCRIPTION:Abstract:Astrophysical plasmas are extraordinary particle acce lerators\, from supernova remnants to the relativistic jets that emanate f rom supermassive black holes and produce very-high-energy cosmic rays and shine across the electromagnetic spectrum. The mechanisms behind these cos mic accelerators remain a long-standing mystery. They are thought to be as sociated with basic plasma processes\, including collisionless shocks and magnetic reconnection\, that control energy dissipation in these systems. These processes involve a complex and nonlinear interplay between the dyna mics of flows\, magnetic fields\, and nonthermal particles that is not yet well understood and affects the observational manifestations of the astro physical environments. I will discuss how the fast progress in computation al and experimental capabilities is creating unique opportunities to push the boundaries of our understanding of the dominant particle acceleration mechanisms by allowing detailed kinetic modeling of different plasma proce sses and controlled laboratory experiments that can help validate these mo dels.Short Bio:Frederico Fiuza is a Senior Staff Scientist and the Theory Group Leader at the High Energy Density Science division at the SLAC Natio nal Accelerator Laboratory. He obtained his PhD degree in Plasma Physics f rom Instituto Superior Tecnico\, Portugal\, in 2012. He then became a Lawr ence Postdoctoral Fellow at the Lawrence Livermore National Laboratory bet ween 2012 and 2015\, before joining SLAC. His research interests span a wi de range of topics in astrophysical and laboratory plasmas\, including par ticle acceleration\, magnetic field amplification\, collisionless shocks\, and magnetic reconnection. Recently\, Fiuza'\;s work on laboratory as trophysics was recognized with the 2018 APS Thomas H. Stix Award for Outst anding Early Career Contributions to Plasma Physics Research and the 2020 APS John Dawson Award for Excellence in Plasma Physics Research. He has al so been awarded the Lawrence Fellowship in 2012\, the European Physical So ciety PhD Research Award in 2013\, and the DOE Early Career Research Progr am Award in 2017. LAST-MODIFIED:20220227T164845Z LOCATION:PA1\, Pavilhão de Matemática URL:http://df.vps.tecnico.ulisboa.pt/eventos/extreme-particle-acceleration -in-astrophysical-plasmas-from-simulations-to-observations-via-laboratory- experiments/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
Astrophysical plasmas are extraordinary pa
rticle accelerators\, from supernova remnants to the relativistic jets tha
t emanate from supermassive black holes and produce very-high-energy cosmi
c rays and shine across the electromagnetic spectrum. The mechanisms behin
d these cosmic accelerators remain a long-standing mystery. They are thoug
ht to be associated with basic plasma processes\, including collisionless
shocks and magnetic reconnection\, that control energy dissipation in thes
e systems. These processes involve a complex and nonlinear interplay betwe
en the dynamics of flows\, magnetic fields\, and nonthermal particles that
is not yet well understood and affects the observational manifestations o
f the astrophysical environments. I will discuss how the fast progress in
computational and experimental capabilities is creating unique opportuniti
es to push the boundaries of our understanding of the dominant particle ac
celeration mechanisms by allowing detailed kinetic modeling of different p
lasma processes and controlled laboratory experiments that can help valida
te these models.
Short Bio:
Frederico Fiuza is a Senio
r Staff Scientist and the Theory Group Leader at the High Energy Density S
cience division at the SLAC National Accelerator Laboratory. He obtained h
is PhD degree in Plasma Physics from Instituto Superior Tecnico\, Portugal
\, in 2012. He then became a Lawrence Postdoctoral Fellow at the Lawrence
Livermore National Laboratory between 2012 and 2015\, before joining SLAC.
His research interests span a wide range of topics in astrophysical and l
aboratory plasmas\, including particle acceleration\, magnetic field ampli
fication\, collisionless shocks\, and magnetic reconnection. Recently\, Fi
uza'\;s work on laboratory astrophysics was recognized with the 2018 A
PS Thomas H. Stix Award for Outstanding Early Career Contributions to Plas
ma Physics Research and the 2020 APS John Dawson Award for Excellence in P
lasma Physics Research. He has also been awarded the Lawrence Fellowship i
n 2012\, the European Physical Society PhD Research Award in 2013\, and th
e DOE Early Career Research Program Award in 2017.
Abstract:
As I am a new postdoc fellow at CENTRA\, I propose to summarise my previ
ous and current main works\, and briefly describe associated future perspe
ctives. This will consist of the discussion of two distinct bodies of work
\, one of them lying in modified gravity (dark energy) and the other one i
n numerical relativity applied to cosmology. First\, I will outline field
theoretical aspects as well as observational constraints and Bayesian mode
l selection studies of a particular class of modified gravity theories\, s
o-called nonlocal gravity theories. In particular\, I will review the rele
vant phenomenology of selected nonlocal models in the light of different c
osmological probes such as the cosmic microwave background\, supernovae\,
large scale structure\, but also future gravitational waves interferometer
s. In a second part\, I will describe my research in numerical relativity
that constitutes an attempt towards the development of a fully general rel
ativistic N-body code for cosmological structure formation.
Abstract:
The future linear e+e- colliders offer a number of unique opportunities for searches for dark matter and dark sector part icles. The collider program itself will offer important capabilities on th ree frontiers: (i) the precision frontier with measurements at the Higgs f actory\, (ii) the energy frontier with direct investigations of the scalar sector\, and (iii) the intensity frontier with fixed-target and beam-dump measurements. In the seminar I will concentrate mostly on (ii) but also c omment on possible experiments in (i) and (iii)\, which altogether address various dark sector portals.
END:VEVENT BEGIN:VEVENT SUMMARY:Nonlocality and Contextuality: Concepts and Applications in Quantu m Information DTSTART:20220304T093000Z DTEND:20220304T110000Z DTSTAMP:20240329T082742Z UID:d105edfe-aa97-4ba2-8ccf-8f3c74012655 SEQUENCE:2 CREATED:20220228T113855Z DESCRIPTION:AbstractIn quantum foundations and quantum information\, under standing the notion of non-cfc.ss/enfi/y is of extreme importance. This te rm broadly characterizes quantum phenomena which not only appear to be at odds with certain instances of classical intuition\, but are provably in c ontradiction with empirical predic- tions of classical theories. The arche typal examples of non-classical phenomena\, produced by operational quantu m mechanics\, are nonlocality and contextuality\, which have traditionally been characterized within a framework of impossibility results\, known as no-go results. Nonlocality and contextuality\, while being at the core of the weirdness and conceptual issues of quantum theory\, also provide usef ul information theoretical resources that can be harnessed for information processing purposes\, for instance\, in quantum computation and quantum c ryp- tography. In this thesis\, we detail various types of non-classical p henomena\, in particular nonlocality and contextuality\, by studying them within the framework of cooperation multiplayer games. This framework prov ides an intuitive way to interpret such no-po results as interactive proto cols where agents try to jointly compute a desired function under a set of operational restrictions. Therein\, the non-classical behaviour particula r to the setup emerges as a resource for appropriately constructed games\, powering the so called gunntutn-over-cla.ssiral advantage — a term whic h succinctly describes that players exploiting the full range of operation al quantum strategies perform better at the game than the players restrict ed to the alternative classical theories. Finally\, we will discuss some a pplications in quantum information\, namely\, within quantum cryptogra- ph y\, where different types of non-classical behaviour are of crucial import ance in order to guarantee security of various protocols. LAST-MODIFIED:20220228T113927Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/nonlocality-and-contextuality -concepts-and-applications-in-quantum-information/ X-ALT-DESC;FMTTYPE=text/html:Abstract
In quantum foundations and quantum information\, understanding the notion of non-cfc.ss/enfi/y is of extreme importance. T his term broadly characterizes quantum phenomena which not only appear to be at odds with certain instances of classical intuition\, but are provabl y in contradiction with empirical predic- tions of classical theories. The archetypal examples of non-classical phenomena\, produced by operational quantum mechanics\, are nonlocality and contextuality\, which have traditi onally been characterized within a framework of impossibility results\, kn own as no-go results. Nonlocality and contextuality\, while being a t the core of the weirdness and conceptual issues of quantum theory\, also provide useful information theoretical resources that can be harnessed fo r information processing purposes\, for instance\, in quantum computation and quantum cryp- tography. In this thesis\, we detail various types of no n-classical phenomena\, in particular nonlocality and contextuality\, by s tudying them within the framework of cooperation multiplayer games. This f ramework provides an intuitive way to interpret such no-po results as inte ractive protocols where agents try to jointly compute a desired function u nder a set of operational restrictions. Therein\, the non-classical behavi our particular to the setup emerges as a resource for appropriately constr ucted games\, powering the so called gunntutn-over-cla.ssiral advantage — a term which succinctly describes that players exploiting the full ran ge of operational quantum strategies perform better at the game than the p layers restricted to the alternative classical theories. Finally\, we will discuss some applications in quantum information\, namely\, within quantu m cryptogra- phy\, where different types of non-classical behaviour are of crucial importance in order to guarantee security of various protocols. p> END:VEVENT BEGIN:VEVENT SUMMARY:Development of a portable magnetic flow cytometer for the detectio n of hospital bacterial infections DTSTART:20220307T100000Z DTEND:20220307T120000Z DTSTAMP:20240329T082742Z UID:93f5dc16-8ff4-469d-b543-f5c2039c5624 SEQUENCE:3 CREATED:20220228T164937Z DESCRIPTION:AbstractThe rising incidence of infectious diseases\, increase d food and water safety concerns\, and the new government initiatives and funding to detect and control antimicrobial-resistant species are demandin g breakthrough advancements in bioanalytical tools for pathogen detection. Moreover\, the clinical prevalence of Pseudomonas aeruginosa\, and Klebsi el/a pneumoniae pathogens underscores the importance of rapid detection ap proaches to contain nosocomial infections and reduce the development of dr ug resistance. Current microbiological detection systems often lack precis ion\, affordability\, and portability. Furthermore\, they require long det ection times\, sophisticated infrastructures\, and trained personnel\, whi ch prevent their applicability at resource-limited settings.In this thesis work\, some of these challenges were addressed by developing a magnetic f low cytometer technology. Flow cytometers have become essential instrument s in biomedical research and routine clinical tests for disease diagnosis \, prognosis\, and treatment monitoring. Magnetic flow cytometers ally the potential for cell detection and counting to the advantages of a lab-on-a -chip technology\, pushing forward the progress in integrated and compact systems for On-site testing. In particul ar\, magnetoresistive sensors (MR ) and magnetic labelling processes were exploited\, promoting high capture efficiencies of magnetically labelled targets and generating strong magne tic fields .The MR chip was integrated with a microfluidic system with a s mall heigh dimension to improve the system sensitivity by promoting the la beled targets to be closer to the sensing units. Chip design optimizations regarding the maximization of the sensor sensitivity and reduction of ele ctromagnetic interferences\, as well as improving the processing signal an alysis and boosting multiplex capabilities were perfo rmed .Protocols for the functionalization of bacteriophages and antibodies onto the magnetic n anoparticles surfaces were optimized and validated for the magnetic labell ing of bacterial cells (K pneumoniae and P aeruginosa) spiked in buffer so lution\, as well as\, directly from clinical rectal swa bs. The results sh owed capture efficiencies over 70 % with specificity.The whole system was integrated with an electronic acquisition setup for the sensors addressing and read-out in collaboration with INESC ID. A signal classificationmetho d based on simulations was proposed to aid in the identification of the nu mber of magnetically labelled bacteria associated with each detection even t\, as well as in the ability to distinguish signatures of free or cluster ed magnetic particles from magnetically labelled targets.This platform was tested and validated for the detection of K/ebsie//a pneumonia in laborat ory samples as well as a pilot study was conducted with clinical rectal sw ab samples collected from 45 patients admitted to the emergency department of Hospital Beatriz Angelo (Loures\, Portugal).Overall\, this work mostly outlies relevant aspects concerning biosensor development\, demonstrating how magnetic flow cytometry can be explored as an accurate\, sensitive\, and portable device that can be applied for bacteria detection and identif ication. LAST-MODIFIED:20220302T144231Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/development-of-a-portable-mag netic-flow-cytometer-for-the-detection-of-hospital-bacterial-infections/ X-ALT-DESC;FMTTYPE=text/html:
Abstract
The rising in cidence of infectious diseases\, increased food and water safety concerns\ , and the new government initiatives and funding to detect and control ant imicrobial-resistant species are demanding breakthrough advancements in bi oanalytical tools for pathogen detection. Moreover\, the clinical prevalen ce of Pseudomonas aeruginosa\, and Klebsiel/a pneumoniae pat hogens underscores the importance of rapid detection approaches to contain nosocomial infections and reduce the development of drug resistance. Curr ent microbiological detection systems often lack precision\, affordability \, and portability. Furthermore\, they require long detection times\, soph isticated infrastructures\, and trained personnel\, which prevent their ap plicability at resource-limited settings.
In this thesis work\, some of these challenges were addressed by developing a magnetic flow cytometer technology. Flow cytometers have become essential instruments in biomedical research and routine clinical tests for disease diagnosis \, prognosis\, and treatment monitoring. Magnetic flow cytomete rs ally the potential for cell detection and counting to the advantages of a lab-on-a-chip technology\, pushing forward the progress in integrated a nd compact systems for On-site testing. In particul ar\, magnetoresistive sensors (MR) and magnetic labelling processes were exploited\, promoting h igh capture efficiencies of magnetically labelled targets and generating s trong magnetic fields .
The MR chip was integ rated with a microfluidic system with a small heigh dimension to improve t he system sensitivity by promoting the labeled targets to be closer to the sensing units. Chip design optimizations regarding the maximization of th e sensor sensitivity and reduction of electromagnetic interferences\, as w ell as improving the processing signal analysis and boosting multiplex cap abilities were perfo rmed .
Protocols for the functionalization of bacteriophages and antibodies onto the magnetic nano particles surfaces were optimized and validated for the magnetic labelling of bacterial cells (K pneumoniae and P aeruginosa ) spiked in buffer solution\, as well as\, directly from clinical rect al swa bs. The results showed capture efficiencies over 70 % with specific ity.
The whole system was integrated with an electronic acquisition setup for the sensors addressing and read-out in co llaboration with INESC ID. A signal classification
method based on simulations was propos ed to aid in the identification of the number of magnetically labelled bac teria associated with each detection event\, as well as in the ability to distinguish signatures of free or clustered magnetic particles from magnet ically labelled targets.
This platform was te sted and validated for the detection of K/ebsie//a pneumonia in lab oratory samples as well as a pilot study was conducted with clinical recta l swab samples collected from 45 patients admitted to the emergency depart ment of Hospital Beatriz Angelo (Loures\, Portugal).
Overall\, this work mostly outlies relevant aspects concerning bio sensor development\, demonstrating how magnetic flow cytometry can be expl ored as an accurate\, sensitive\, and portable device that can be applied for bacteria detection and identification.
END:VEVENT BEGIN:VEVENT SUMMARY:From quarks and gluons to hadrons and multiquarks DTSTART:20220308T160000Z DTEND:20220308T180000Z DTSTAMP:20240329T082742Z UID:3e67338e-6e7f-4885-94d0-75d81925dabf SEQUENCE:2 CREATED:20220218T201347Z DESCRIPTION: LAST-MODIFIED:20220218T205927Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/from-quarks-and-gluons-to-had rons-and-multiquarks/ END:VEVENT BEGIN:VEVENT SUMMARY:FlexibleDecay: An automated calculator of scalar decay widths DTSTART:20220309T143000Z DTEND:20220309T160000Z DTSTAMP:20240329T082742Z UID:640bc510-dd16-4a06-b30c-5891ce3689e8 SEQUENCE:1 CREATED:20220304T161014Z DESCRIPTION: Abstract:I will present FlexibleDecay\, a tool to calculate d ecays of scalars in an arbitrary BSM model. The tool aims for high precisi on particularly in the case of Higgs boson decays. In the case of scalar a nd pseudoscalar Higgs boson decays the known higher order SM QED\, QCD and EW effects are taken into account where possible. The program works in a modified MSbar scheme that exhibits a decoupling property with respect to heavy BSM physics\, with BSM parameters themselves treated in the MSbar/DR bar-scheme allowing for an easy connection to high scale tests for\, e.g.\ , perturbativity and vacuum stability\, and the many observable calculatio ns readily available in MSbar/DRbar programs. Pure BSM effects are taken i nto account at the leading order\, including all one-loop contributions to loop-induced processes. The program is implemented as an extension to Fle xibleSUSY\, which determines the mass spectrum for arbitrary BSM models\, and does not require any extra configuration from the user. LAST-MODIFIED:20220304T161014Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/flexibledecay-an-automated-ca lculator-of-scalar-decay-widths/ X-ALT-DESC;FMTTYPE=text/html: Abstract:
<
/b>
I will present FlexibleDecay\, a tool to calculate decays of scalars in an arbitrary BSM model. The tool aims for h igh precision particularly in the case of Higgs boson decays. In the case of scalar and pseudoscalar Higgs boson decays the known higher order SM QE D\, QCD and EW effects are taken into account where possible. The program works in a modified MSbar scheme that exhibits a decoupling property with respect to heavy BSM physics\, with BSM parameters themselves treated in t he MSbar/DRbar-scheme allowing for an easy connection to high scale tests for\, e.g.\, perturbativity and vacuum stability\, and the many observable calculations readily available in MSbar/DRbar programs. Pure BSM effects are taken into account at the leading order\, including all one-loop contr ibutions to loop-induced processes. The program is implemented as an exten sion to FlexibleSUSY\, which determines the mass spectrum for arbitrary BS M models\, and does not require any extra configuration from the user.
END:VEVENT BEGIN:VEVENT SUMMARY:Plasma dynamics in extreme fields: challenges and opportunities DTSTART:20220309T160000Z DTEND:20220309T180000Z DTSTAMP:20240329T082742Z UID:6ecd1d9c-4659-4954-8c8a-ccdf1567f318 SEQUENCE:4 CREATED:20220227T164623Z DESCRIPTION:Title: Plasma dynamics in extreme fields: challenges and oppor tunitiesAbstract: The next generation of lasers will access intensities ab ove 10^23 W/cm^2. When plasmas or relativistic electron beams interact wit h these lasers\, energy loss due to radiation emission\, or quantum effect s such as electron-positron pair creation become important for their dynam ics. Repeated occurrence of pair creation can induce a so-called “QED ca scade”\, that generates an exponentially rising number of particles. Thi s allows for creating exotic plasmas that are a mix of electrons\, ions\, positrons\, energetic photons and intense background fields. Extreme laser -plasma interactions can be explored to form optical traps\, create&\;a ccelerate particles and produce novel radiation sources. I will introduce a QED module coupled with the particle-in-cell framework OSIRIS that allow s studying nonlinear plasma dynamics in the transition from the classical to the quantum-dominated regime of interaction. Studies relevant for (near ) future experiments will be discussed.Short Bio: Marija Vranic obtained h er MSc degree from University of Belgrade\, Serbia and her PhD at Institut o Superior Tecnico in Lisbon\, Portugal. After PhD\, she was working in Ex treme Light Infrustructure in Prague\, Czech Republic\, and then returned to Portugal. Her research is focused on plasmas in extreme conditions\, wh ere quantum effects can affect the collective plasma dynamics. She combine s analytical theory and massively parallel computer simulations to perform the studies relevant for state-of-the-art and near-future laser experimen ts using the most intense lasers in the world. Marija is a winner of the i nternational John Dawson PhD thesis prize (best PhD thesis worldwide in th e field of plasma-based accelerators) and the IBM Scientific Prize. As a P I\, she was awarded 250k€ R&\;D grant by FCT and several internationa l supercomputing grants (a combined >\; 200 milion CPUh). LAST-MODIFIED:20220302T213341Z LOCATION:PA1\, Pavilhão de Matemática URL:http://df.vps.tecnico.ulisboa.pt/eventos/plasma-dynamics-in-extreme-fi elds-challenges-and-opportunities/ X-ALT-DESC;FMTTYPE=text/html:Title: Plasm a dynamics in extreme fields: challenges and opportunities
Abstract: The next gene ration of lasers will access intensities above 10^23 W/cm^2. When plasmas or relativistic electron beams interact with these lasers\, energy loss du e to radiation emission\, or quantum effects such as electron-positron pai r creation become important for their dynamics. Repeated occurrence of pai r creation can induce a so-called “QED cascade”\, that generates an ex ponentially rising number of particles. This allows for creating exotic pl asmas that are a mix of electrons\, ions\, positrons\, energetic photons a nd intense background fields. Extreme laser-plasma interactions can be exp lored to form optical traps\, create&\;accelerate particles and produce novel radiation sources. I will introduce a QED module coupled with the p article-in-cell framework OSIRIS that allows studying nonlinear plasma dyn amics in the transition from the classical to the quantum-dominated regime of interaction. Studies relevant for (near) future experiments will be di scussed.
Sho rt Bio: Marija Vranic obtained her MSc degree from University of Belgr ade\, Serbia and her PhD at Instituto Superior Tecnico in Lisbon\, Portuga l. After PhD\, she was working in Extreme Light Infrustructure in Prague\, Czech Republic\, and then returned to Portugal. Her research is focused o n plasmas in extreme conditions\, where quantum effects can affect the col lective plasma dynamics. She combines analytical theory and massively para llel computer simulations to perform the studies relevant for state-of-the -art and near-future laser experiments using the most intense lasers in th e world. Marija is a winner of the international John Dawson PhD thesis pr ize (best PhD thesis worldwide in the field of plasma-based accelerators) and the IBM Scientific Prize. As a PI\, she was awarded 250k€ R&\;D g rant by FCT and several international supercomputing grants (a combined &g t\; 200 milion CPUh).
END:VEVENT BEGIN:VEVENT SUMMARY:Gravitational waves from primordial fluctuations DTSTART:20220310T143000Z DTEND:20220310T160000Z DTSTAMP:20240329T082742Z UID:fc668eac-6e6c-4fd7-8bdc-1ae26b897461 SEQUENCE:2 CREATED:20220307T110027Z DESCRIPTION:Abstract:The evolution of primordial fluctuations in the early universe is accompanied by a production of gravitational waves. The so-ca lled induced gravitational waves are the cosmic messenger of primordial fl uctuations on the smallest scales\, which may have been generated during c osmic inflation. In this talk\, I will discuss how they may be used to exp lore the early universe'\;s initial conditions and expansion history. This includes gravitational waves induced by oscillatory features in the p rimordial spectrum\, early isocurvature fluctuations and a primordial blac k hole dominated universe. LAST-MODIFIED:20220307T110110Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/gravitational-waves-from-prim ordial-fluctuations/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
b>The evolution of primordial fluctuations in the early universe is accomp
anied by a production of gravitational waves. The so-called induced gravit
ational waves are the cosmic messenger of primordial fluctuations on the s
mallest scales\, which may have been generated during cosmic inflation. In
this talk\, I will discuss how they may be used to explore the early univ
erse'\;s initial conditions and expansion history. This includes gravi
tational waves induced by oscillatory features in the primordial spectrum\
, early isocurvature fluctuations and a primordial black hole dominated un
iverse.
Abstract
The subject of this thesis is the analysis of s ecure asymmetric cryptographic schemes\, and the study of the main resourc e for information processing protocols\, the total\, classical and quantum multipartite correlations.
Motivated by the usefulness of secure multiparty computation as a privacy-protecting data a nalysis tool\, we proposed a practical quantum realization of randomized o blivious transfer. Our solution is aimed at targeting the limitations of s ecurity and efficiency faced by the classical schemes for oblivious transf er. A detailed security proof was written for the protocol. We also provid e preliminary results of performance from an experimental setup based on a n entangled photons source and polarization encoding.
The impossibility results for achieving unconditionally secure bi t commitment have driven the research for secure solutions under several d ifferent assumptions. We propose a criteria for ranking the complexity of such assumptions\, together with new functionality\, called the asymmet ric quantum beamer\, which is minimal under the listed c riteria. Using this new assumption we develop a universally composable bit commitment protocol with linear com plexity in its security parameter.< /p>
Based on previous work for a correlation hier archy for probability distributions\, we for malize a framework of corre lation structures for quantum systems. We explore some of its mathematical properties\, computational complexity\, use for information compression o f quantum states\, and some aspects of categorization of correlations by t he way they are dis tributed as well as by their nature (classical/quant um). Additionally\, we present a practical application for the correlation structures framework for early classification of time series data sets. T he proposed method is based on selectively cutting correlations that are n ot directly connected to the class variable until a criterion of optimalit y is satisfied. The algorithm was able to successfully guess the class of test data from real world sources using only a few initial time steps. Its versatility for application for other problems is highlighted.
Finally\, we lay the foundations of a quantum algorithm ic complexity theory based on the dc-QTM model. We conclude that\, althoug h the algorithmic complexity of a physical state and its classical descrip tion are equivalent\, they can be differentiated while taking the role of a resource to compute another state. Additionally\, we prove that the chai n rule does not hold for this version of algorithmic complexity and argue how that result can be used to define the complexity of correlations in qu antum systems.
END:VEVENT BEGIN:VEVENT SUMMARY:Applications of black hole scattering DTSTART:20220317T143000Z DTEND:20220317T163000Z DTSTAMP:20240329T082742Z UID:83a4751f-8933-481b-9f7c-de3b07f0daae SEQUENCE:1 CREATED:20220314T151143Z DESCRIPTION:Abstract:In this talk\, I will describe scattering in the pres ence of black holes. I will try to convince you thati) there is a new regi me in the phase space of quantum gravity where scattering amplitudes can r eliably be calculated in the low energy theory\,ii) Hawking'\;s free f ield theory breaks down after Page time (implying information retrieval in local effective field theory)\, and thatiii) there is an emergent soft li mit near the horizon\, resulting in new soft graviton theorems in the pres ence of black holes.Finally\, I will conclude with some more applic ations. LAST-MODIFIED:20220314T151143Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/applications-of-black-hole-sc attering/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
In this talk\, I will describe scattering in the presence of black holes
. I will try to convince you that
i) there is a new regime in the phas
e space of quantum gravity where scattering amplitudes can reliably be cal
culated in the low energy theory\,
ii) Hawking'\;s free field theo
ry breaks down after Page time (implying information retrieval in local ef
fective field theory)\, and that
iii) there is an emergent soft limit
near the horizon\, resulting in new soft graviton theorems in the presence
of black holes.
Finally\, I will conclude with some more appli
cations.
Symmetries are at the core of our understanding and description
of most physical phenomena across all accessible energy scales\, from the
organization of the structures at the largest distances in the Universe t
o the physics governing the fundamental interactions of subatomic particle
s. The focus of my talk will be on gravitational theories. I will show exa
mples of Goldstone bosons in cosmology and discuss the role of non-linearl
y realized symmetries of gravity. I will then present recent developments
in the context of symmetries of black holes and their relevance for gravit
ational-wave astronomy.
Bio: I obtained my Ph.D. from Scuola Normale Superiore\, Pisa\, in 2016. I was then a postdoctoral research scientist first at Utrecht University and la ter at Columbia University. I am currently a research fellow at the Intern ational Centre for Theoretical Physics (ICTP) in Trieste. My primary resea rch interests and my main original scientific contributions are in the con text of effective field theories\, theoretical cosmology and black holes.< /p>
END:VEVENT BEGIN:VEVENT SUMMARY:Hidden Symmetries of Gravity DTSTART:20220324T143000Z DTEND:20220324T160000Z DTSTAMP:20240329T082742Z UID:f5b5129e-6fcd-4122-8523-d01f437578df SEQUENCE:1 CREATED:20220321T103658Z DESCRIPTION:Abstract:I will discuss classes of hidden symmetries of gravit y and their consequences for black holes and compact objects. It is well k nown that asymptotically flat black holes in general relativity have a van ishing static tidal response (i.e.\, zero Love numbers). In the talk\, I w ill first show that this is the result of a hidden structure of ladder sym metries governing static (spin 0\,1\,2) perturbations around black holes\, and I will discuss the underlying geometric origin. I will also present e xamples of hidden symmetries and dualities at finite frequency and their c onsequences for quasinormal modes. I will finally briefly present an effec tive field theory for perturbations around black holes in scalar-tensor th eories and discuss how to connect the effective couplings to possible devi ations in the observed ringdown frequencies. LAST-MODIFIED:20220321T103658Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/hidden-symmetries-of-gravity/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
I will discuss classes of hidden symmetries of gravity and their consequ
ences for black holes and compact objects. It is well known that asymptoti
cally flat black holes in general relativity have a vanishing static tidal
response (i.e.\, zero Love numbers). In the talk\, I will first show that
this is the result of a hidden structure of ladder symmetries governing s
tatic (spin 0\,1\,2) perturbations around black holes\, and I will discuss
the underlying geometric origin. I will also present examples of hidden s
ymmetries and dualities at finite frequency and their consequences for qua
sinormal modes. I will finally briefly present an effective field theory f
or perturbations around black holes in scalar-tensor theories and discuss
how to connect the effective couplings to possible deviations in the obser
ved ringdown frequencies.
Abstract:
With recent experimental evidence for tetr
aquarks and pentaquarks\, hadron spectroscopy is nowadays a cutting-edge a
rea of research with the LHC among its central facilities. Hadrons are bou
nd states of quarks and gluons in QCD\, the theory of the strong interacti
on\, but their spectrum and structure are much richer than the naïve quar
k model suggests and governed by nonperturbative phenomena such as confine
ment and dynamical mass generation.
In this colloquium I will mak
e a survey through some open questions in QCD\, with an emphasis on the st
ructure of exotic hadrons and multiquarks\, and connect them with the key
underlying phenomena of mass generation for quarks and gluons. I will high
light recent advances with functional methods\, which allow one to compute
hadron properties from first principles. Systematic improvements in this
approach have made it possible to address a wide range of problems from mu
ltiquark spectroscopy to form factors\, parton distributions\, the anomalo
us magnetic moment of the muon\, and the QCD phase diagram.
Sh
ort Bio:
My research is centered around nonperturbative phenomena
in QCD and nuclear and hadron physics\, including hadron and multiquark sp
ectroscopy and structure\, Compton scattering and the muon g-2 problem. I
obtained my PhD degree at the University of Graz (Austria) and carried out
research stays at Argonne National Laboratory (USA)\, TU Darmstadt\, and
the University of Giessen (Germany). In 2017 I moved to IST Lisboa within
an FCT Investigator Grant\, and in 2020 our group NPStrong joined LIP.
Title: Searc hing for Habitable Worlds: Challenges &\; Opportunities
Speaker: Prof. Lisa Kaltenegger\, Director of the Carl Sagan Institute at Cornell University\, NY\, USA
Abstract : More than 5000 detected extrasolar planets have shown us the huge di versity of these new worlds: among the surprising discoveries are hot plan ets orbiting their star in only a few hours\, lava worlds\, Mini-Neptunes as well as the first potential rocky worlds in the temperate Habitable Zon e of their host stars.
Observation techniques have already reached the sensitivity to explore the chemical composition of the atmospheres of some hot exoplanets. With the successful launch of t he James Webb Space Telescope\, we will be able to glimpse into the atmosp here of potentially habitable worlds orbiting other stars.
For now\, our own planet is our only key to spot life in the universe. Its evolution through time and its diverse biota give us clues on what to search for. The spectra of planets are our window to explore po tential habitable worlds lightyears away - as well as to understand our ow n planet better. This talk will present the newest results in our search\, its challenges and opportunities on the way to finding out whether or not we are alone in the cosmos.
END:VEVENT BEGIN:VEVENT SUMMARY:Testing the nature of dark compact objects and dark matter with gr avitational waves DTSTART:20220407T143000Z DTEND:20220407T160000Z DTSTAMP:20240329T082742Z UID:3df9658a-4e0d-4e4e-b0e9-6f7d78aaef79 SEQUENCE:1 CREATED:20220405T092905Z DESCRIPTION:Abstract:The direct observation of gravitational waves already allowed us to directly observe hundreds of dark ultracompact objects (mos t likely black holes) that were entirely invisible to us until very recent ly. As remarkable as this feat already is\, these observations only mark t he beginning of what lays ahead. Planned future gravitational-wave detecto rs promise to make gravitational-wave physics a precision\, data-driven sc ience field\, which will make it possible to address (and possibly open ne w) outstanding problems in various areas of physics and astronomy but also potentially opening the door to unexpected discoveries.With this motivati on in mind\, in this talk I propose to summarise some of my past and curre nt work that aims at tackling questions such as: how well do the black hol e solutions predicted by General Relativity explain the dark compact objec ts we observe with gravitational waves? Are there other more exotic compac t objects in the Universe? Is dark matter composed of particles\, such as axions or dark photons? In particular\, I will (i) discuss how the multipo lar structure of compact objects can be inferred through gravitational wav e observations\, focusing on recent work where we computed the corrections to the dynamics of a binary system due to generic\, nonaxisymmetric mass quadrupole moments to leading post-Newtonian order and (ii) (time permitti ng) shortly discuss current and future prospects for gravitational-wave ob servations to directly constrain the existence of ultralight boson fields\ , which have been proposed as strong dark matter candidates. LAST-MODIFIED:20220405T092905Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/testing-the-nature-of-dark-co mpact-objects-and-dark-matter-with-gravitational-waves/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
The direct observation of gravitational waves already allowed us to dire
ctly observe hundreds of dark ultracompact objects (most likely black hole
s) that were entirely invisible to us until very recently. As remarkable a
s this feat already is\, these observations only mark the beginning of wha
t lays ahead. Planned future gravitational-wave detectors promise to make
gravitational-wave physics a precision\, data-driven science field\, which
will make it possible to address (and possibly open new) outstanding prob
lems in various areas of physics and astronomy but also potentially openin
g the door to unexpected discoveries.
With this motivation in mind\, i
n this talk I propose to summarise some of my past and current work that a
ims at tackling questions such as: how well do the black hole solutions pr
edicted by General Relativity explain the dark compact objects we observe
with gravitational waves? Are there other more exotic compact objects in t
he Universe? Is dark matter composed of particles\, such as axions or dark
photons? In particular\, I will (i) discuss how the multipolar structure
of compact objects can be inferred through gravitational wave observations
\, focusing on recent work where we computed the corrections to the dynami
cs of a binary system due to generic\, nonaxisymmetric mass quadrupole mom
ents to leading post-Newtonian order and (ii) (time permitting) shortly di
scuss current and future prospects for gravitational-wave observations to
directly constrain the existence of ultralight boson fields\, which have b
een proposed as strong dark matter candidates.
Sumário:
Brain research is now r esorting to nanotechnology in order to create efficient devices for neuron al recording. Typical extracellular microelectrodes present sub-optimal el ectrical coupling between neurons and electrodes. The goal of this work is to present novel 3D architectures to maximize the interaction between ele ctrodes and the neuronal network\, and to demonstrate the viability of 3D in-depth neural recordings\, providing a major breakthrough in the field. To this end\, an electrical model of the neuron-electron coupling is to be developed and simulated\, followed by the elaboration and implementation of a protocol for 3D electrode micro/nanofabrication. The demonstration of the fabricated device will be performed by growing a neuronal culture on the array and acquiring electrical measurements. The outcome of this proje ct will enable neuronal data acquisition in 3D networks\, greatly benefitt ing the study of neuronal systems and advancing our understanding of neuro nal functional diseases.
END:VEVENT BEGIN:VEVENT SUMMARY:Problems in the Foundations of Physics DTSTART:20220420T160000Z DTEND:20220420T170000Z DTSTAMP:20240329T082742Z UID:a427b021-020c-4be6-a618-2e17f4e237db SEQUENCE:4 CREATED:20220311T233023Z DESCRIPTION:Title: Problems in the Foundations of PhysicsAbstract: In the foundations of physics\, we have long-standing open problems such as the nature of dark matter and dark energy\, the hierarchy problem\, or th e missing quantization of gravity. Yet physicists have not made progress o n solving those problems for 50 years. In this talk\, I discuss how phy sicists ended up in a vicious cycle of theorizing and null results\, and w hat we can do to overcome the present phase of stagnation. LAST-MODIFIED:20220311T233450Z LOCATION:Online\, zoom URL:http://df.vps.tecnico.ulisboa.pt/eventos/problems-in-the-foundations-o f-physics/ X-ALT-DESC;FMTTYPE=text/html:Title: Probl ems in the Foundations of Physics
Abstract: In the foundations of physics\, we have long-standing open problems such as the nature of dark matter and d ark energy\, the hierarchy problem\, or the missing quantization of gravit y. Yet physicists have not made progress on solving those problems for 5 0 years. In this talk\, I discuss how physicists ended up in a vicious cy cle of theorizing and null results\, and what we can do to overcome the pr esent phase of stagnation.
END:VEVENT BEGIN:VEVENT SUMMARY:Black holes in grand canonical ensemble DTSTART:20220421T143000Z DTEND:20220421T160000Z DTSTAMP:20240329T082742Z UID:37cc304a-67bc-4ae4-ae66-26e1760f719f SEQUENCE:1 CREATED:20220413T103900Z DESCRIPTION:ABSTRACT: From the successful works of Bekenstein and Hawking\ , it is known that black holes are thermodynamic objects. In particular\, black holes emit particles as a black body at the Hawking temperature\, an d have a precise entropy\, the Bekenstein-Hawking entropy. The nature of t he entropy of a black hole is still an open problem\, a possible explanati on may lie on a theory of quantum gravity. In this seminar\, I will talk a bout the construction of the canonical and grand canonical ensemble for bl ack hole spacetimes using the path integral approach to quantum gravity. S uch ensembles determine the thermodynamics of a black hole from a semiclas sical approximation of the quantum theory. The seminar is planned as follo ws: (i) I will summarize previous works\, from Gibbons and Hawking\, to Yo rk and André and Lemos\; (ii) I will then describe the results of my curr ent work on the grand canonical ensemble of d-dimensional ReissnerNordstr öm black holes in a cavity and compare them to the case of a charged cond ucting sphere in flat d-dimensional spacetime in a cavity. LAST-MODIFIED:20220413T103900Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/black-holes-in-grand-canonica l-ensemble/ X-ALT-DESC;FMTTYPE=text/html:ABSTRACT: From the successful works of Bekenstein and Hawking\, it is known that black holes are thermodynamic objects. In particular\, black holes emit particles as a black body at the Hawking temperature\, and have a precise entropy\, the Bekenstein-Hawking entropy. The nature of the entropy of a black hole is s till an open problem\, a possible explanation may lie on a theory of quant um gravity. In this seminar\, I will talk about the construction of the ca nonical and grand canonical ensemble for black hole spacetimes using the p ath integral approach to quantum gravity. Such ensembles determine the the rmodynamics of a black hole from a semiclassical approximation of the quan tum theory. The seminar is planned as follows: (i) I will summarize previo us works\, from Gibbons and Hawking\, to York and André and Lemos\; (ii) I will then describe the results of my current work on the grand canonical ensemble of d-dimensional ReissnerNordström black holes in a cavity and compare them to the case of a charged conducting sphere in flat d-dimensio nal spacetime in a cavity.
END:VEVENT BEGIN:VEVENT SUMMARY:Fink broker\, an optimized recommendation system for transient fol low-up DTSTART:20220422T143000Z DTEND:20220422T163000Z DTSTAMP:20240329T082742Z UID:0100e939-95e6-4d28-a1e8-e30f17e5653b SEQUENCE:1 CREATED:20220422T091324Z DESCRIPTION: ABSTRACT: Next generation experiments such as the Vera Rubin Observatory Legacy Survey of Space and Time (LSST) will provide an unprece dented volume of time-domain data opening a new era of big data in astrono my. To fully harness the power of these surveys\, we require analysis meth ods capable of dealing with large data volumes that can identify promising transients within minutes for follow-up coordination. In this talk I will describe the infrastructure put in place by LSST to handle approximately 10 million transient candidates per night and present Fink\, a broker deve loped to face these challenges. Fink is based on high-end technology and d esigned for fast and efficient analysis of big flows. It has been chosen a s one of the official LSST brokers and will receive the full data stream. I will highlight the state-of-the-art machine learning techniques used to generate early classification scores for a variety of time-domain phenomen a including kilonovae and supernovae\, as well as for artifacts\, like sat ellites glitches. Such methods include Deep Learning advances and Active L earning approaches to coherently incorporate available information\, deliv ering increasingly more accurate added values throughout the duration of t he survey. I will also highlight the potential for discovery of new catego ries of sources and how we can optimize for discovery in the era of LSST. LAST-MODIFIED:20220422T091324Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/fink-broker-an-optimized-reco mmendation-system-for-transient-follow-up/ X-ALT-DESC;FMTTYPE=text/html:ABSTRACT: Next gen eration experiments such as the Vera Rubin Observatory Legacy Survey of Sp ace and Time (LSST) will provide an unprecedented volume of time-domain da ta opening a new era of big data in astronomy. To fully harness the power of these surveys\, we require analysis methods capable of dealing with lar ge data volumes that can identify promising transients within minutes for follow-up coordination. In this talk I will describe the infrastructure pu t in place by LSST to handle approximately 10 million transient candidates per night and present Fink\, a broker developed to face these challenges. Fink is based on high-end technology and designed for fast and efficient analysis of big flows. It has been chosen as one of the official LSST brok ers and will receive the full data stream. I will highlight the state-of-t he-art machine learning techniques used to generate early classification s cores for a variety of time-domain phenomena including kilonovae and super novae\, as well as for artifacts\, like satellites glitches. Such methods include Deep Learning advances and Active Learning approaches to coherentl y incorporate available information\, delivering increasingly more accurat e added values throughout the duration of the survey. I will also highligh t the potential for discovery of new categories of sources and how we can optimize for discovery in the era of LSST.
END:VEVENT BEGIN:VEVENT SUMMARY:Towards the detection of ultra-low energetic neutrinos with plasma metamaterials DTSTART:20220426T140000Z DTEND:20220426T160000Z DTSTAMP:20240329T082742Z UID:e1c63719-114a-48e2-bbad-b2cecdd43c10 SEQUENCE:2 CREATED:20220422T144720Z DESCRIPTION: AbstractTheoretical works showed the existence of neutrino f lux with energy below eV\, the detection of these low energetic neutrino c an shed light on Dark Matter problem along with the improvement of the Sta ndard Model\; the detector used nowadays are not able to detect such energ ies\, in this thesis we propose a technique to detect slow flux of massive neutrino by plasmon generation. Through the semiclassical approximation o f the Weak Interaction\, we derived the force felt by a plasma due to the neutrino distribution\, and vice-versa\; therefore\, by the Kinetic descri ption with linear perturbation approach\, we studied the interaction of el ectron plasma and neutrino flux. The long lifetime of plasmon in graphene structures oriented us to study bidimensional (2D) electron systems\; the Weak interaction\, between neutrino and ungated electron solid-state plasm a\, leads to a feature alike the beam-plasma instability\, raising the pos sibility to have a growth rate. The generated plasmon has Wavevector depen dent on the neutrino velocity and spectral width function of the neutrino ’s density and mass\; the instability was considered in an effective tri dimensional (3D) metamaterial obtained by graphene heterostructure\, the r esulting Signal to Noise ratio (SN) is mainly dependent on the length of t he device. Larger growth rates are found for lower neutrino energy and lar ger density: with detector size in the order of centimeters\, the detectio n of neutrino with energy µeV is ensured for flux above 105 cm−2 with S N about 10 dB\, for meV neutrino the same SN is ensured for flux above 101 2 cm−2 . LAST-MODIFIED:20220422T154025Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/towards-the-detection-of-ultr a-low-energetic-neutrinos-with-plasma-metamaterials/ X-ALT-DESC;FMTTYPE=text/html:
Abstract
Theoretical work s showed the existence of neutrino flux with energy below eV\, the detecti on of these low energetic neutrino can shed light on Dark Matter problem a long with the improvement of the Standard Model\; the detector used nowada ys are not able to detect such energies\, in this thesis we propose a tech nique to detect slow flux of massive neutrino by plasmon generation. Throu gh the semiclassical approximation of the Weak Interaction\, we derived th e force felt by a plasma due to the neutrino distribution\, and vice-versa \; therefore\, by the Kinetic description with linear perturbation approac h\, we studied the interaction of electron plasma and neutrino flux. The l ong lifetime of plasmon in graphene structures oriented us to study bidime nsional (2D) electron systems\; the Weak interaction\, between neutrino an d ungated electron solid-state plasma\, leads to a feature alike the beam- plasma instability\, raising the possibility to have a growth rate. The ge nerated plasmon has Wavevector dependent on the neutrino velocity and spec tral width function of the neutrino’s density and mass\; the instability was considered in an effective tridimensional (3D) metamaterial obtained by graphene heterostructure\, the resulting Signal to Noise ratio (SN) is mainly dependent on the length of the device. Larger growth rates are foun d for lower neutrino energy and larger density: with detector size in the order of centimeters\, the detection of neutrino with energy µeV is ensur ed for flux above 105 cm−2 with SN about 10 dB\, for meV neutrino the sa me SN is ensured for flux above 1012 cm−2 .
END:VEVENT BEGIN:VEVENT SUMMARY:Black Holes and Dark Matter DTSTART:20220505T143000Z DTEND:20220505T160000Z DTSTAMP:20240329T082742Z UID:20d9b53b-b9a3-46ca-be99-c70407f7e459 SEQUENCE:1 CREATED:20220502T143242Z DESCRIPTION: Abstract:The discovery of gravitational wave signals from mer ger events of massive binary-black-hole (BBH) systems have prompted a rene wed debate in the scientific community about the interplay between Black H ole phenomenology and Dark Matter searches. On the one hand\, Black Holes of primordial origin (PBHs) may have formed in the early Universe and coul d constitute a significant portion of the elusive dark matter that\, accor ding to standard cosmology\, makes up the majority of the matter content i n the universe. On the other hand\, peculiar classes of Black Holes can be studied as "\;portals"\; to Dark Matter detection in the Gravitat ional Wave channel\, due to the large density of DM that is expected to be present around them. In the first part of the talk\, I will review the mo st promising multi-messenger avenues towards detection of PBHs. I will fir st focus on the radio/X-ray band\, and present the prospects of discovery for both a hypothetical PBH population and the guaranteed population of as trophysical isolated black holes in our Galaxy\, based on the broad-band e mission from the interstellar gas that is being accreted onto them. Then\, I will turn my attention to the gravitational wave domain\, and discuss t he merger rate of black-hole binaries. I will present a detailed evaluatio n of the expected rate from a generic (subdominant) component of PBHs\, an d analyze the role of future observation at high redshift to identify a pr imordial component on top of the rate associated to astrophysical BHs. In the final part of my talk\, I will turn my attention to the impact of Dark Matter overdensities around Intermediate-Mass Black Holes\, and on their impact on the gravitational waveform emitted in presence of an Intermediat e-Mass-Ratio inspiral. I will demonstrate that the dephasing effect induce d by the presence of the DM is observable in this channel\, and the proper ties of the DM overdensity can be measured by the upcoming LISA observator y. LAST-MODIFIED:20220502T143242Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/black-holes-and-dark-matter/ X-ALT-DESC;FMTTYPE=text/html: Abstract:
The
discovery of gravitational wave signals from merger events of massive bina
ry-black-hole (BBH) systems have prompted a renewed debate in the scientif
ic community about the interplay between Black Hole phenomenology and Dark
Matter searches. On the one hand\, Black Holes of primordial origin (PBHs
) may have formed in the early Universe and could constitute a significant
portion of the elusive dark matter that\, according to standard cosmology
\, makes up the majority of the matter content in the universe. On the oth
er hand\, peculiar classes of Black Holes can be studied as "\;portals
"\; to Dark Matter detection in the Gravitational Wave channel\, due t
o the large density of DM that is expected to be present around them. In t
he first part of the talk\, I will review the most promising multi-messeng
er avenues towards detection of PBHs. I will first focus on the radio/X-ra
y band\, and present the prospects of discovery for both a hypothetical PB
H population and the guaranteed population of astrophysical isolated black
holes in our Galaxy\, based on the broad-band emission from the interstel
lar gas that is being accreted onto them. Then\, I will turn my attention
to the gravitational wave domain\, and discuss the merger rate of black-ho
le binaries. I will present a detailed evaluation of the expected rate fro
m a generic (subdominant) component of PBHs\, and analyze the role of futu
re observation at high redshift to identify a primordial component on top
of the rate associated to astrophysical BHs. In the final part of my talk\
, I will turn my attention to the impact of Dark Matter overdensities arou
nd Intermediate-Mass Black Holes\, and on their impact on the gravitationa
l waveform emitted in presence of an Intermediate-Mass-Ratio inspiral. I w
ill demonstrate that the dephasing effect induced by the presence of the D
M is observable in this channel\, and the properties of the DM overdensity
can be measured by the upcoming LISA observatory.
Abstract:
A possible implication of a sub-eV scalar dark matter (DM) field interacting with the Standard Mo del (SM) is oscillations of fundamental constants. Here\, I will talk abou t how to establish the direct experimental bounds on the coupling of an os cillating DM to the SM using spectroscopy and/or various quantum sensors ( DDM search). The equivalence principle (EP) violating tests can also be us ed to constrain the existence of a light scalar. Furthermore\, I will disc uss about the complementarity between the EP violating tests and DDM searc hes. We will further explore the challenges of a quadratically coupled lig ht DM in the context of naturalness and how to probe such models.
END:VEVENT BEGIN:VEVENT SUMMARY:Quasi-Disorder Effects in Topological Superconductors DTSTART:20220509T151500Z DTEND:20220509T173000Z DTSTAMP:20240329T082742Z UID:2ffe4ef4-a247-43ba-891d-93bdc5ccb2a1 SEQUENCE:2 CREATED:20220504T145725Z DESCRIPTION:Resumo:Estudamos os efeitos da desordem de Aubry-André e deso rdem de Anderson para um modelo de um supercondutor topológico bidimensio nal com um campo magnético externo. São estudados os casos de um superco ndutor de emparelhamento tipo p e um supercondutor não centrossimétrico com mistura de emparelhamentos de tipo p e s e com acoplamento spin-órbit a de Rashba. Revemos as propriedades topológicas do sistema sem desordem\ , que dependem da direção do campo magnético (perpendicular ou paralelo ao plano do supercondutor). O sistema desordenado é estudado tanto no es paço real como num espaço misto.Quando o campo magnético é paralelo\, estudamos os efeitos de quasi-desordem e desordem\, aplicada tanto nas fro nteiras como no interior do supercondutor\, e discutimos os seus efeitos n a localização do sistema\, densidade de estados e nas funções de onda\ , numa abordagem no espaço real. Ainda no espaço real mostramos que\, pa ra um campo magnético perpendicular\, a introdução de quasi-desordem le va ao aparecimento de novas regiões topológicas\, caracterizadas por um valor inteiro do número de Chern.Numa abordagem no espaço misto\, identi ficamos novos regimes com o aparecimento de novas bandas planas de Majoran a e também novos estados de fronteira de Majorana unidirecionais\, com a introdução de quasi-desordem. Mostramos que as bandas planas de Majorana têm uma fase Berry quantizada de π e indentificamo-la como um invariant e topológico. Duas transições topológicas são identificadas e os valo res dos expoentes críticos z e ν são obtidos. A natureza fractal dos es tados é discutida tanto para desordem de Anderson como para desordem de A ubry-André. LAST-MODIFIED:20220504T145853Z LOCATION:Sala P3 Pavilhão de Matemática\, Piso 1/ Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/quasi-disorder-effects-in-top ological-superconductors/ X-ALT-DESC;FMTTYPE=text/html:Resumo:
Estudamos os efeito s da desordem de Aubry-André e desordem de Anderson para um modelo de um supercondutor topológico bidimensional com um campo magnético externo. S ão estudados os casos de um supercondutor de emparelhamento tipo p e um supercondutor não centrossimétrico com mistura de emparelhamentos de tipo p e s e com acoplamento spin-órbita de Rashba. Reve mos as propriedades topológicas do sistema sem desordem\, que dependem da direção do campo magnético (perpendicular ou paralelo ao plano do supe rcondutor). O sistema desordenado é estudado tanto no espaço real como n um espaço misto.
Quando o campo magnético é paralelo\, estudamos os efeitos de quasi-desordem e desordem\, aplicada tanto nas fronteiras como no interior do supercondutor\, e discutimos os seus efeitos na localização do sistema\, densidade de estados e nas fun ções de onda\, numa abordagem no espaço real. Ainda no espaço real mos tramos que\, para um campo magnético perpendicular\, a introdução de qu asi-desordem leva ao aparecimento de novas regiões topológicas\, caracte rizadas por um valor inteiro do número de Chern.
Numa abordagem no espaço misto\, identificamos novos regimes com o a parecimento de novas bandas planas de Majorana e também novos estados de fronteira de Majorana unidirecionais\, com a introdução de quasi-desorde m. Mostramos que as bandas planas de Majorana têm uma fase Berry quantiza da de π e indentificamo-la como um invariante topológico. Duas tr ansições topológicas são identificadas e os valores dos expoentes crí ticos z e ν são obtidos. A natureza fractal dos estados é discutida tanto para desordem de Anderson como para desordem de Aubry-And ré.
END:VEVENT BEGIN:VEVENT SUMMARY:Quantum Horizons and the Emergence of Gravity and Space-Time DTSTART:20220511T160000Z DTEND:20220511T180000Z DTSTAMP:20240329T082742Z UID:db10176c-60cf-4b3f-bf94-a2423727d4ad SEQUENCE:7 CREATED:20220311T234450Z DESCRIPTION:Abstract: Event horizons may occur near black holes\, in flat space or in a cosmological spacetimes. In the last decade important prog ress has been in the understanding of the quantum properties of the horizo ns. These advances have revealed a deep connection between thermodynamics\ , quantum entanglement\, and the emergence of the laws of gravitation.Even the fabric of spacetime itself has to be viewed as being emergent from a microscopic quantum mechanical description. In this colloquium I will revi ew these developments and explain the recent insights on the black hole in formation paradox.Subsequently I will discuss the generalization and impli cations of these ideas to flat space and cosmological spacetimes. I will e nd with a discussion of possible observational consequences. LAST-MODIFIED:20220506T194612Z LOCATION:PA1\, Pavilhão de Matemática URL:http://df.vps.tecnico.ulisboa.pt/eventos/quantum-horizons-and-emergenc e/ X-ALT-DESC;FMTTYPE=text/html:Abstract: Event horizons may occur near black holes\, in flat space or in a cosmological spacetimes. In the last decade importan t progress has been in the understanding of the quantum properties of the horizons. These advances have revealed a deep connection between thermodyn amics\, quantum entanglement\, and the emergence of the laws of gravitatio n.
Even the fabric of spacetime itself has to be viewed as being emergent from a microscopic quantum mechanical descrip tion. In this colloquium I will review these developments and explain the recent insights on the black hole information paradox.
Subsequently I will discuss the generalization and implications
of these ideas to flat space and cosmological spacetimes. I will end with
a discussion of possible
observational consequences.
Resumo:
A natureza difusa de matéria bosónica ultraleve e o
seu fraco acoplamento ao modelo standard torna o seu estudo possível quas
e exclusivamente através dos seus efeitos gravitacionais.
A descobert
a do fenómeno da Superradiância em torno de buracos negros faz deles os
laboratórios ideais para estudar as propriedades destes possíveis consti
tuintes da Matéria negra.
O fenómeno da superradiância\, análogo a
o famoso processo de Penrose para ondas\, permite que campos escalares ext
raiam energia rotacional de buracos negros\, abrandando a sua rotação\,
e assim deixando marcas observacionais claras que permitem colocar limites
na massa de tais campos.
A superradiância em torno buracos negros te
m vindo a ser alvo de extensos estudos na última década. Contrasta esse
com o estudo de campos escalares em sistemas binários de buracos negros\,
onde o nosso conhecimento fica ainda a desejar. O crescente número de de
tecções de ondas gravitacionais provenientes de sistemas binários de ob
jectos compactos e o desenvolvimento da nova geração de detectores torna
imprescindível perceber como podem estes campos escalares moldar evoluç
ão e dinâmica de tais sistemas.
Ao preservar as principais caracter
ísticas de tais sistemas astrofísicos\, o estudo de modelos-análogos of
erece-nos uma via para melhor entender a sua dinâmica. Através de result
ados quantitativos e qualitativos o estudo de tais modelos permite também
perceber como novos dados experimentais podem ser utilizados para entende
r a natureza e desvendar as propriedades destes campos.
ABSTRACT: Predicti ons for the properties of the Milky Way (MW) satellite galaxies are crucia l tests for competing dark matter models. Deviations from the cold and col lisionless picture of dark matter\, such as free-streaming\, dark acoustic oscillations\, and self-interactions between dark matter particles\, modi fy predictions for the number of MW satellite galaxies and/or for their de nsities. Calculating accurate predictions is complicated by the large arra y of factors relevant to satellite formation and processing\, including th e stochasticity of MW halo formation\, the difficulties in modelling satel lite stripping with limited resolution\, and for contraction of the host h alo through cooling baryons\, to name but a few. In this talk I will use t he COCO N-body simulations of MWanalogue systems to make estimates for the MW satellite population properties in three models: cold dark matter (CDM )\, a warm dark matter model (WDM) with a thermal relic mass of 3.3keV\, a nd a self-interacting dark matter model (SIDM) that enables gravothermal c ollapse. I will use these models to predict the range of viable subhalo ho sts for ~33 observed MW satellites\, and then discuss how future observati ons will enable us to ascertain which model best describes the properties of dark matter.
END:VEVENT BEGIN:VEVENT SUMMARY:The Science of Climate Change DTSTART:20220518T160000Z DTEND:20220518T180000Z DTSTAMP:20240329T082742Z UID:5fa910d1-0928-4fad-87f1-22136328333d SEQUENCE:8 CREATED:20220203T073404Z DESCRIPTION:Abstract: A brief historical perspective of climate change sci ence since the publication of Joseph Fourier'\;s papers on the greenho use effect up to the development of General Circulation Models and the mor e accurate prediction of climate change as a result of anthropogenic emiss ions of greenhouse gases by Syukuro Manabe and Klaus Hasselmann and the co nnection of their work to Giorgio Parisi'\;s contributions to the theo ry of disordered materials and random processes\, will be presented. The p resent world situation as regards climate change and its future evolution will be discussed. Finally an overview of the main climate change impacts now and in the future in Europe and in Portugal will be presented. LAST-MODIFIED:20220509T102926Z LOCATION:PA1\, Pavilhão de Matemática URL:http://df.vps.tecnico.ulisboa.pt/eventos/the-science-of-climate-change / X-ALT-DESC;FMTTYPE=text/html:Abstract: A brief historical perspective of climate chan ge science since the publication of Joseph Fourier'\;s papers on the g reenhouse effect up to the development of General Circulation Models and t he more accurate prediction of climate change as a result of anthropogenic emissions of greenhouse gases by Syukuro Manabe and Klaus Hasselmann and the connection of their work to Giorgio Parisi'\;s contributions to th e theory of disordered materials and random processes\, will be presented. The present world situation as regards climate change and its future evol ution will be discussed. Finally an overview of the main climate change im pacts now and in the future in Europe and in Portugal will be presented. p> END:VEVENT BEGIN:VEVENT SUMMARY:Explosive transients\, their origins and their use to study the hi gh-redshift Universe DTSTART:20220519T143000Z DTEND:20220519T160000Z DTSTAMP:20240329T082742Z UID:325da54c-9dd5-4d94-baa9-aaad7f9dd928 SEQUENCE:1 CREATED:20220516T094756Z DESCRIPTION: Abstract:Explosive transients are usually connected to massiv e stars\, directly or indirectly. Some of the most luminous of those explo sions are gamma-ray bursts (GRBs) and superluminous supernovae (SLSNe). GR Bs come in two different classes\, long GRBs whose progenitors are massive stars with low metallicity and high rotation rate\, and short GRBs\, the merger of two compact objects and one of the known sources of gravitationa l wave signals. Type I SLSNe (without H in their spectra) were first thoug ht to have progenitors similar to long GRBs\, but studies of the host gala xies have suggested more extreme stars for those events. Due to their rare numbers and the fact that they are hosted mostly in dwarf galaxies we wil l likely not be able to observe the progenitor systems of any of these eve nts before explosion in the near future. In this talk I will review what w e know about the progenitors of different stellar explosions and how we us e the host galaxy and environment to get indirect information on the proge nitor\, in particular using 3D spectroscopy. One important aspect is where the star-formation originates giving rise to the progenitors and I will f ocus on a peculiar\, nearby\, host galaxy where we have multi-wavelength d ata to study possible star-formation processes. I will also present how we can use in particular GRBs to study the ISM in high-redshift galaxies wit h absorption lines in the afterglow spectrum and present the first metalli city measurement of a short GRB host. Finally\, I will review how and if w e might be able to use these explosions to test the expansion of the Unive rse. LAST-MODIFIED:20220516T094756Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/explosive-transients-their-or igins-and-their-use-to-study-the-high-redshift-universe/ X-ALT-DESC;FMTTYPE=text/html:
Abstract:
Expl
osive transients are usually connected to massive stars\, directly or indi
rectly. Some of the most luminous of those explosions are gamma-ray bursts
(GRBs) and superluminous supernovae (SLSNe). GRBs come in two different c
lasses\, long GRBs whose progenitors are massive stars with low metallicit
y and high rotation rate\, and short GRBs\, the merger of two compact obje
cts and one of the known sources of gravitational wave signals. Type I SLS
Ne (without H in their spectra) were first thought to have progenitors sim
ilar to long GRBs\, but studies of the host galaxies have suggested more e
xtreme stars for those events. Due to their rare numbers and the fact that
they are hosted mostly in dwarf galaxies we will likely not be able to ob
serve the progenitor systems of any of these events before explosion in th
e near future. In this talk I will review what we know about the progenito
rs of different stellar explosions and how we use the host galaxy and envi
ronment to get indirect information on the progenitor\, in particular usin
g 3D spectroscopy. One important aspect is where the star-formation origin
ates giving rise to the progenitors and I will focus on a peculiar\, nearb
y\, host galaxy where we have multi-wavelength data to study possible star
-formation processes. I will also present how we can use in particular GRB
s to study the ISM in high-redshift galaxies with absorption lines in the
afterglow spectrum and present the first metallicity measurement of a shor
t GRB host. Finally\, I will review how and if we might be able to use the
se explosions to test the expansion of the Universe.
Abstract:
The geometrical formulation of gravity eme
rges naturally from the equivalence principle\, hinting toward an intrigui
ng connection with the concepts of mass and inertia. As already observed b
y Einstein\, General Relativity can be expressed in a variety of ways\, in
cluding not only the most common metric approach but also the Palatini\, t
eleparallel\, and Einstein-Cartan formulations. These realizations differ
mainly in their choice of fundamental degrees of freedom\, being otherwise
mathematically equivalent as pure gravity is concerned. The degeneracy am
ong different gravity incarnations breaks down\, however\, in the presence
of non-minimal couplings to matter\, as happens unavoidably when accounti
ng for the Standard Model Higgs. This opens the possibility of testing the
nature of gravity with cosmological observations. In this talk\, I will p
rovide an overview of this fascinating paradigm\, describing its predictio
ns\, generalizations\, open questions\, and implications for the infamous
hierarchy problem.
Abstract:
Spectra with full towers of levels are expected due to the quantization of the string vibrations\, however different theoreti cal models exist for the excitation spectra. First principle computations are important to test the different models and to search for novel phenome na\, but so far only a few excited states of QCD flux tubes have been stud ied with pure gauge SU(3) lattice QCD in 3+1 dimensions. We thus aim to st udy a spectrum of flux tubes with static quark and antiquark sources up to a significant number of excitations. In this thesis\, we compute the exci tation of the flux tube for quantum numbers Λ η =Σ+ g \,Σ− g \, Σ+ u \, Σ− u \, Πg\,Πu\, ∆g\, ∆u\, where for some of them just the ground state or up to two levels were calculated and published in the lite rature. To achieve the highest possible excitation level\, we construct a large set of operators with the correct symmetry\, solve the generalized e igenvalue problem and compare the results of different lattice QCD gauge a ctions with different lattice spacings and anisotropies.
END:VEVENT BEGIN:VEVENT SUMMARY:The predictive power of numerical relativity DTSTART:20220526T143000Z DTEND:20220526T160000Z DTSTAMP:20240329T082742Z UID:d4ae05e9-0310-4117-9095-1653e5965de5 SEQUENCE:1 CREATED:20220524T100718Z DESCRIPTION: Abstract:Numerical relativity plays many important roles in astrophysics andgeneral relativity. For example\, it plays an important role inconstructing theoretical templates of gravitation al waves which arecrucial for detecting gravitational waves and e xtracting the physicalparameters of gravitational-wave sources. In this talk\, I will introduceour latest numerical-relativity simulat ions for neutron-star mergerspaying particular attention to the nu cleosynthesis of heavy elements andto a rotating stellar collapse leading to a black hole that couldaccompany a supernova-like ex plosion\, for the prediction of forthcomingobservational results. LAST-MODIFIED:20220524T100718Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/the-predictive-power-of-numer ical-relativity/ X-ALT-DESC;FMTTYPE=text/html: Abstract:
Nume
rical relativity plays many important roles in astrophysics and
general relativity. For example\, it plays an important role in
constructing theoretical templates of gravitational waves which
are
crucial for detecting gravitational waves and extracting
the physical
parameters of gravitational-wave sources. In this
talk\, I will introduce
our latest numerical-relativity simulati
ons for neutron-star mergers
paying particular attention to the
nucleosynthesis of heavy elements and
to a rotating stellar
collapse leading to a black hole that could
accompany a super
nova-like explosion\, for the prediction of forthcoming
observat
ional results.
Resumo
A Mat
éria Escura (ME) é uma pedra angular do nosso entendimento do Universo.
A validade do modelo ΛCDM implica que as galáxias estão rodeadas por um
halo de matéria massiva e não bariónica\, cujas interações continuam
a eludir os nossos esforços experimentais. Caso estas partículas intera
jam com a matéria bariónica\, elas vão acumular no interior das estrela
s\, onde subsequentes interacções com o plasma estelar poderão causar e
feitos na estrutura e na evolução destas estrelas. O estudo destes efeit
os é importante por duas razões: por um lado\, pode contribuir para o no
sso conhecimento acerca de física estelar\; por outro\, os efeitos podem
ser testados contra observações de alta precisão com o objectivo de lim
itar as propriedades da ME. Nesta Tese estudamos a fenomenologia das inter
ações de ME numa variedade de estrelas e assumindo o paradigma de partí
culas massivas com fracas interações (WIMP). Ao considerar diferentes ti
pos de estrelas podemos tirar partido dos diferentes processos físicos qu
e as caracterizam para explorar novas formas de estudar ME usando observa
ções astronómicas. Para completar esta tarefa criámos um módulo que p
ermite modelar todos os processos relacionados com ME durante a evoluçao
estelar. Este módulo funciona em conjunto com um código de evolução es
telar open-source\, e juntos formam um laboratório único onde podemos te
star as hipóteses propostas nesta Tese. Usando estas ferramentas estudamo
s três cenários astrofísicos: o impacto do transporte de energia por ME
assimétrica na estrutura e evolução de estrelas de baixa massa da sequ
ência principal\; os efeitos da produção de energia pela aniquilação
de ME no centro de estrelas do ramo das gigantes vermelhas\; e o impacto d
e interacções de ME na astrosismologia de estrelas do agrupamento vermel
ho. Ainda estudamos as incertezas presentes na modelação do espaço de f
ase do halo de ME e o seu impacto nos estudos referidos acima. No geral\,
obtivemos o resultado que enquanto que atuais limitações experimentais r
eduzem a capacidade dos métodos propostos nesta Tese de competirem com ex
periências concebidas para estudar a ME directamente\, desenvolvimentos n
um futuro próximo desbloquearão o potencial único de estrelas como labo
ratórios de ME. Para finalizar\, notamos ainda que a versatilidade das fe
rramentos numéricas desenvolvidas nesta Tese permite que o módulo possa
ser melhorado e usado para estudar aplicações para além das estudadas n
esta Tese.
Abstract:
The mass of the W boson\, a mediator of the weak force between elementary particles\, is tightly constrained by the symmetries o f the standard model of particle physics. The Higgs boson was the last mis sing component of the model. After the observation of the Higgs boson\, a measurement of the W boson mass provides a stringent test of the model. We measure the W boson mass using data corresponding to 8.8 inverse femtobar ns of integrated luminosity collected in proton-antiproton collisions at a 1.96 TeV center-of-mass energy with the CDF II detector at the Fermilab T evatron collider. The measured value is in tension with the prediction of the model.
END:VEVENT BEGIN:VEVENT SUMMARY:Black-Hole Neutron Star Simulations with BAM code DTSTART:20220602T143000Z DTEND:20220602T160000Z DTSTAMP:20240329T082742Z UID:5d77ad9e-9f02-402b-8ebb-6d370c6508b5 SEQUENCE:1 CREATED:20220530T090210Z DESCRIPTION:Abstract:With the first detections of black hole-neutron star (BHNS) mergers (GW200105 and GW200115) by the LIGO-Virgo-Kagra Collaborati on a significant scientific breakthrough was achieved. The physical interp retation of pre-and postmerger signals requires careful cross-examination between observational and theoretical modelling results. In this talk\, I will briefly introduce the BAM numerical relativity code and its capabilit ies in simulating compact object mergers. I will then present our work on simulating excision initial data (ID) of BHNS binary constructed using the publicly available LORENE ID solver and evolved using moving puncture gau ge choices. Constrained solved and consistent ID are essential in accurate ly modeling compact object systems and a wider coverage of the parameter s pace is needed in exploring the dynamics of such systems. In this regard a nd with the availability of robust ID solvers like FUKA (public) and Ellip tica (inhouse) we are able to explore a wider parameter space with accurat e ID. Finally\, I will report some improvements in the simulations using I D from these solvers. LAST-MODIFIED:20220530T090210Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/black-hole-neutron-star-simul ations-with-bam-code/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
With
the first detections of black hole-neutron star (BHNS) mergers (GW200105 a
nd GW200115) by the LIGO-Virgo-Kagra Collaboration a significant scientifi
c breakthrough was achieved. The physical interpretation of pre-and postme
rger signals requires careful cross-examination between observational and
theoretical modelling results. In this talk\, I will briefly introduce the
BAM numerical relativity code and its capabilities in simulating compact
object mergers. I will then present our work on simulating excision initia
l data (ID) of BHNS binary constructed using the publicly available LORENE
ID solver and evolved using moving puncture gauge choices. Constrained so
lved and consistent ID are essential in accurately modeling compact object
systems and a wider coverage of the parameter space is needed in explorin
g the dynamics of such systems. In this regard and with the availability o
f robust ID solvers like FUKA (public) and Elliptica (inhouse) we are able
to explore a wider parameter space with accurate ID. Finally\, I will rep
ort some improvements in the simulations using ID from these solvers.
A pesquisa relatad a neste manuscrito é dedicada ao estudo da dinâmica turbulenta que surge em átomos ultra-frios em condições de propagação incoerente de luz. Átomos frios são produzidos numa armadilha magneto-óptica iluminada por seis feixes de laser independentes. Para iluminação quase ressonante\, os átomos interagem uns com os outros por processos frequentes de absorç ão e reemissão de fotões\, que são espalhados várias vezes. À medida que o detuning dos lasers de arrefecimento e aprisionamento é aproximada da transição eletrônica\, a propagação da luz torna-se aleatória\, resultando num aprisionamento eficaz de radiação. Em tais condições\, o fluido atômico é remexido por complexas dinâmicas espaço-temporais. A densidade atômica nos regimes estável e turbulento é examinada por me io duma técnica pumpprobe que desenvolvemos ad-hoc. O objetivo deste diag nóstico é superar as limitações devidas à integração da linha de vi são que são comuns em métodos normais de espalhamento e absorção. Ass im\, somos capazes de visualizar diretamente a distribuição de densidade interna da nuvem atômica e caracterizar a sua estrutura espacial. Neste manuscrito descrevemos com precisão a configuração da diagnóstica e os princípios de funcionamento\, e detalhamos os procedimentos experimentai s e de análise que permitem investigar a estrutura local das flutuações da densidade atômica. As observações são então comparadas com as sol uções analíticas para o modelo de turbulência de bolhas de fotões em átomos frios. Este modelo teórico é apoiado por simulações numéricas que permitem estender a sua validade para nuvens não homogêneas. Os res ultados experimentais são consistentes com a descrição da turbulência impulsionada pela radiação difusiva e que se desenvolve no fundo do arre fecimento e aprisionamento dos lasers. A dinâmica turbulenta surge do cre scimento e colapso contínuo das bolhas de fotões: a estrutura local de d ensidade média é caracterizada por um tamanho bem definido\, exibindo as sim\, notavelmente\, uma distribuição estatística não Kolmogorov. Esta tese contribui para fortalecer a analogia fluidodinâmica entre sistemas astrofísicos dominados por pressão de radiação e átomos ultrafrios pr oduzidos em armadilhas magneto-ópticas. Essa semelhança pode ser útil p ara testar tanto as previsões de modelos complexos de plasma espacial qua nto as técnicas sofisticadas aplicadas às medições de objetos espaciai s.
END:VEVENT BEGIN:VEVENT SUMMARY:Core-collapse and binary mergers in scalar-GaussBonnet gravity DTSTART:20220609T143000Z DTEND:20220609T160000Z DTSTAMP:20240329T082742Z UID:78817063-65bb-4d4e-88a1-f6d9a624316c SEQUENCE:2 CREATED:20220603T105039Z DESCRIPTION:ABSTRACT: In the present talk\, we will discuss the dynamics o f spontaneous scalarization of black holes and neutron stars in scalar-Gau ss-Bonent gravity. We will focus on two particularly interesting nonlinear and highly dynamical scenarios for (de)scalarization - binary black hole merger and stellar core collapse. The gravitational wave signatures that a re a smoking gun of the (de)scalarization will be discussed. LAST-MODIFIED:20220603T105124Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/core-collapse-and-binary-merg ers-in-scalar-gaussbonnet-gravity/ X-ALT-DESC;FMTTYPE=text/html:ABSTRACT: In the pr esent talk\, we will discuss the dynamics of spontaneous scalarization of black holes and neutron stars in scalar-Gauss-Bonent gravity. We will focu s on two particularly interesting nonlinear and highly dynamical scenarios for (de)scalarization - binary black hole merger and stellar core collaps e. The gravitational wave signatures that are a smoking gun of the (de)sca larization will be discussed.
END:VEVENT BEGIN:VEVENT SUMMARY:How to Talk to a Science Denier DTSTART:20220615T160000Z DTEND:20220615T170000Z DTSTAMP:20240329T082742Z UID:e9c02d7a-2e11-48a1-8bb2-700ee9bb05f1 SEQUENCE:8 CREATED:20220404T175701Z DESCRIPTION:Title:How to Talk to a Science DenierAbstract:It'\;s somet imes claimed that trying to convince a science denier with facts will only backfire. The latest research\, however\, shows that this is mistaken and that there ARE effective techniques that can be used to keep someone from becoming a science denier and even help them to overturn mistaken beliefs once they are formed. The secret lies in recognizing that even empirical beliefs may be held for reasons that have nothing to do with evidence\, su ch as personal values\, trust\, ideology\, and group identity. The best wa y to convince someone in this case is not to berate them\, or clobber them with evidence\, but engage in an examination of the cognitive and normati ve reasons why they reject factual evidence in the first place.Zoom Link:h ttps://videoconf-colibri.zoom.us/j/82812777433?pwd=NE9idksvcmphNWlmRHJOZFF BUjF2QT09 LAST-MODIFIED:20220405T080250Z LOCATION:Online\, zoom URL:http://df.vps.tecnico.ulisboa.pt/eventos/how-to-talk-to-a-science-deni er/ X-ALT-DESC;FMTTYPE=text/html:Title:
How to Talk to a Science Denier
Abstract:
It'\;s someti mes claimed that trying to convince a science denier with facts will only backfire. The latest research\, however\, shows that this is mistaken and that there ARE effective techniques that can be used to keep someone from becoming a science denier and even help them to overturn mistaken beliefs once they are formed. The secret lies in recognizing that even empirical b eliefs may be held for reasons that have nothing to do with evidence\, suc h as personal values\, trust\, ideology\, and group identity. The best way to convince someone in this case is not to berate them\, or clobber them with evidence\, but engage in an examination of the cognitive and normativ e reasons why they reject factual evidence in the first place.
Zoom Link:
https://videoconf-colibri.zoom.us/j/82812777433?pwd=NE9idksvcm phNWlmRHJOZFFBUjF2QT09
END:VEVENT BEGIN:VEVENT SUMMARY:Family symmetries and Flavour DTSTART:20220615T160000Z DTEND:20220615T180000Z DTSTAMP:20240329T082742Z UID:e534687a-4cc2-4a90-8904-45414e0fed21 SEQUENCE:2 CREATED:20220615T105647Z DESCRIPTION:Abstract: I review the Flavour problem of the Standard Model and then discuss the most promising solution\, family symmetries. I presen t how this type of symmetries can solve the flavour problem of the Standar d Model and other extensions Beyond the Standard Model. LAST-MODIFIED:20220615T105804Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/family-symmetries-and-flavour / X-ALT-DESC;FMTTYPE=text/html:Abstract:
I review the Flavour problem of the Standard Mo del and then discuss the most promising solution\, family symmetries. I pr esent how this type of symmetries can solve the flavour problem of the Sta ndard Model and other extensions Beyond the Standard Model.
END:VEVENT BEGIN:VEVENT SUMMARY:Synchronized bosonic hair: equilibrium solutions DTSTART:20220621T140000Z DTEND:20220621T160000Z DTSTAMP:20240329T082742Z UID:137ae405-303c-4eb4-94eb-b0e5be0eb057 SEQUENCE:1 CREATED:20220620T092428Z DESCRIPTION: Resumo:Bosonic fields can spin down rotating black holes (BHs ) via superradiance. If massive\, they may remain trapped in the vicinity of a BH and endow it with hair co-rotating in synchrony with the event hor izon. An illustrative example of this mechanism is the family of BHs with synchronized hair\, that can co-exist with Kerr BHs and emerge dynamically from them at some scales. In this talk\, I will first explore the feature s of BHs with vanishingly little (scalar and vector) hair\, drawing their similarity to the atomic orbitals of the electron in a hydrogen atom. Then \, I will discuss how hairy such BHs can become from the growth and satura tion of superradiant instabilities. Finally\, I will show how massless bos onic fields can also bind to BHs and form synchronized clouds. LAST-MODIFIED:20220620T092428Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/synchronized-bosonic-hair-equ ilibrium-solutions/ X-ALT-DESC;FMTTYPE=text/html:
Resumo:
Bosonic fields can spin down rotating black
holes (BHs) via superradiance. If massive\, they may remain trapped in th
e vicinity of a BH and endow it with hair co-rotating in synchrony with th
e event horizon. An illustrative example of this mechanism is the family o
f BHs with synchronized hair\, that can co-exist with Kerr BHs and emerge
dynamically from them at some scales. In this talk\, I will first explore
the features of BHs with vanishingly little (scalar and vector) hair\, dra
wing their similarity to the atomic orbitals of the electron in a hydrogen
atom. Then\, I will discuss how hairy such BHs can become from the growth
and saturation of superradiant instabil
itie s. Finally\, I will show how massless bosonic fields can also bind to BHs and form synchronized clouds.
END:VEVENT BEGIN:VEVENT SUMMARY:Defect and strain profiles caused by ion implantation in GaN DTSTART:20220621T150000Z DTEND:20220621T170000Z DTSTAMP:20240329T082742Z UID:92dc8a81-c5bc-4c23-ab10-425214f9ffd2 SEQUENCE:1 CREATED:20220620T083108Z DESCRIPTION: ResumoO Nitreto de Gálio (GaN) é um semicondutor de hiato largo\, com alta mobilidade eletrónica e alto campo de disrupção. Estas características permitem a operação em regimes de alta tensão\, tempe ratura e frequência\, tornando o GaN muito desejado na área da eletróni ca de potência. A manipulação de algumas das suas características pode ser obtida através de implantação iónica. Apesar das suas vantagens\, esta técnica implica a criação de defeitos e tensão no material\, pre judicando o seu funcionamento e eficiência. Implantação iónica com eur ópio (Eu) e silício (Si) foi feita em amostras de GaN\, com o objetivo d e estudar os efeitos da mesma. A evolução de danos e de tensão com a fl uência foram estudados usando Retrodispersão de Rutherford em modo de Ca nalização\, e Difração de Raios-X\, respetivamente. Métodos analític os e computacionais foram usados para extrair os perfis de defeitos e tens ão com a profundidade. Medidas de stress in-situ foram feitas nas amostra s implantadas com Si de modo a estudar a evolução do stress.Os perfis de defeitos obtidos são concordantes entre diferentes técnicas\, e consist entes com os perfis de tensão\, para ambas implantações. A evolução d os perfis com a fluência de implantação sugere transformações de defe itos\, nomeadamente de defeitos pontuais para estruturas de defeitos mais complexas. Estes processos estão associados à relaxação do stress e da tensão\, observados tanto nos perfis de tensão como nos resultados do s tress. Modelos quantitativos e qualitativos para a evolução de danos e s tress no material são propostos\, com base nos resultados obtidos experim entalmente. LAST-MODIFIED:20220620T083108Z LOCATION:Sala QA1.1 - Pavilhão de Química URL:http://df.vps.tecnico.ulisboa.pt/eventos/defect-and-strain-profiles-ca used-by-ion-implantation-in-gan/ X-ALT-DESC;FMTTYPE=text/html:
Resumo
O Nitreto de Gálio (GaN) é um semicondutor de hiato largo\, com alta mobilidade eletrónica e alto campo de disrupção. Estas características permitem a operação em regimes de alta tensão\, temperatura e frequência\, tornando o GaN m uito desejado na área da eletrónica de potência. A manipulação de alg umas das suas características pode ser obtida através de implantação i ónica. Apesar das suas vantagens\, esta técnica implica a criação de d efeitos e tensão no material\, prejudicando o seu funcionamento e eficiê ncia.
Implantação iónica com európio (Eu ) e silício (Si) foi feita em amostras de GaN\, com o objetivo de estudar os efeitos da mesma. A evolução de danos e de tensão com a fluência f oram estudados usando Retrodispersão de Rutherford em modo de Canalizaç ão\, e Difração de Raios-X\, respetivamente. Métodos analíticos e com putacionais foram usados para extrair os perfis de defeitos e tensão com a profundidade. Medidas de stress in-situ foram feitas nas amostras implantadas com Si de modo a estudar a evolução do stress.
Os perfis de defeitos obtidos são concordantes entre dife rentes técnicas\, e consistentes com os perfis de tensão\, para ambas im plantações. A evolução dos perfis com a fluência de implantação sug ere transformações de defeitos\, nomeadamente de defeitos pontuais para estruturas de defeitos mais complexas. Estes processos estão associados à relaxação do stress e da tensão\, observados tanto nos perfis de ten são como nos resultados do stress. Modelos quantitativos e qualitativos p ara a evolução de danos e stress no material são propostos\, com base n os resultados obtidos experimentalmente.
END:VEVENT BEGIN:VEVENT SUMMARY:Multi-Higgs Doublet Models DTSTART:20220622T090000Z DTEND:20220622T110000Z DTSTAMP:20240329T082742Z UID:d8d8ac82-1c96-4f1d-8cd2-a3bac800e9c2 SEQUENCE:1 CREATED:20220620T083344Z DESCRIPTION: AbstractThis thesis is aimed at the study of softly-broken $ A_4$ or $S_4$ 3 Higgs Doublet Models. Regarding these\, two topics are dis cussed. In the first they are studied via the introduction of parameters t hat softly break the respective symmetries but preserve the directions of the vacuum expectation values of the triplet. Within this regime\, we firs t conduct an analysis of the masses of physical states\, highlighting comm on properties in the mass spectra of the extended scalar sector. Beyond th is\, we focus on the decay properties of these particles\, with the goal o f identifying dark matter candidates. We have identified a particular case where these candidates are accommodated without any further restrictions on the model.The second topic concerns an adaptation of a geometric method so that it suits softly-broken potentials. We discuss aspects to be taken into account so that our proposed method can be successful.This is then e xemplified in an application to the softly-broken $S_4$ symmetric potentia l with general diagonal soft-breaking parameters. We conduct a complete de termination of all the possible neutral minima the model can have in these circumstances\, as well as necessary conditions for these minima to occur . LAST-MODIFIED:20220620T083344Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/multi-higgs-doublet-models/ X-ALT-DESC;FMTTYPE=text/html:
Abstract
This thesis is aimed at the study of softly-broken $A_4$ or $S_4$ 3 Higgs Doublet Models. Regardi ng these\, two topics are discussed.
In the first they are studied via the introduction of parameters that softly brea k the respective symmetries but preserve the directions of the vacuum expe ctation values of the triplet. Within this regime\, we first conduct an an alysis of the masses of physical states\, highlighting common properties i n the mass spectra of the extended scalar sector. Beyond this\, we focus o n the decay properties of these particles\, with the goal of identifying d ark matter candidates. We have identified a particular case where these ca ndidates are accommodated without any further restrictions on the model. p>
The second topic concerns an adaptation of a g eometric method so that it suits softly-broken potentials. We discuss aspe cts to be taken into account so that our proposed method can be successful .
This is then exemplified in an application to the softly-broken $S_4$ symmetric potential with general diagonal soft- breaking parameters. We conduct a complete determination of all the possib le neutral minima the model can have in these circumstances\, as well as n ecessary conditions for these minima to occur.
END:VEVENT BEGIN:VEVENT SUMMARY:Wind has its satellite: aeolus DTSTART:20220622T160000Z DTEND:20220622T170000Z DTSTAMP:20240329T082742Z UID:675268ae-a77c-428c-a3df-5ed87874fda1 SEQUENCE:4 CREATED:20220411T141031Z DESCRIPTION:The colloquium will focus on the European Space Agency'\;s aeolus satellite. It will more generally address satellite engineering. a eolus was placed into orbit by a Vega rocket on August 22\, 2018\, from Ko urou in French Guiana. Its mission is to measure the speed of the winds al l around the Earth and up to 30 kilometers in altitude. The mission is a w orld first\, completed and a success. The data is great and is daily used for weather forecast. We will share a bit of the history\, emotions and sc ientific and technical knowledge of aeolus. The basic principles of aeolus are simple and can be understood by everyone without any prior technical or scientific knowledge. The conference will cover the mission of aeolus\, the orbit and its constraints\, some technical elements of the constructi on of aeolus\, the principles of measurement\, the telescope\, the laser\, some of the major difficulties and how they were resolved. We will talk a bout terminator\, cargo\, soap bubbles\, red lights\, Lego\, pressure cook er\, black light\, magnetic field detector possibly. LAST-MODIFIED:20220515T002302Z LOCATION:PA1\, Pavilhão de Matemática URL:http://df.vps.tecnico.ulisboa.pt/eventos/wind-has-its-satellite-aeolus / X-ALT-DESC;FMTTYPE=text/html:The colloquium will focus on the European Space Agency'\;s aeolus satellite. It will more generally address satellite engineering. aeolus was placed into orbit by a Vega rocket on August 22\, 2018\, from Kourou in French Guiana. Its miss ion is to measure the speed of the winds all around the Earth and up to 30 kilometers in altitude. The mission is a world first\, completed and a su ccess. The data is great and is daily used for weather forecast. We will s hare a bit of the history\, emotions and scientific and technical knowledg e of aeolus. The basic principles of aeolus are simple and can be understo od by everyone without any prior technical or scientific knowledge. The co nference will cover the mission of aeolus\, the orbit and its constraints\ , some technical elements of the construction of aeolus\, the principles o f measurement\, the telescope\, the laser\, some of the major difficulties and how they were resolved. We will talk about terminator\, cargo\, soap bubbles\, red lights\, Lego\, pressure cooker\, black light\, magnetic fie ld detector possibly.
END:VEVENT BEGIN:VEVENT SUMMARY:The conformal Killing spinor initial data equations DTSTART:20220623T143000Z DTEND:20220623T163000Z DTSTAMP:20240329T082742Z UID:c72e7512-09dd-48ca-b4c2-6dc89e598115 SEQUENCE:1 CREATED:20220620T091844Z DESCRIPTION: Abstract:We obtain necessary and sufficient conditions for an initial data set for the vacuum conformal Einstein field equations to giv e rise to a spacetime development in possession of a Killing spinor. The f act that the conformal Einstein field equations are used in our derivation allows for the possibility of the initial hypersurface intersecting non-t rivially with (or even being a subset of) null infinity. For conciseness\, these conditions are derived assuming that the initial hypersurface is sp acelike. Hence\, in particular\, these conformal Killing spinor initial da ta equations encode necessary and sufficient conditions for the existence of a Killing spinor in the development of asymptotic initial data on space like components of null infinity. LAST-MODIFIED:20220620T091844Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/the-conformal-killing-spinor- initial-data-equations/ X-ALT-DESC;FMTTYPE=text/html:Abstract:We obtain necessary and sufficient conditions for an initial data set f or the vacuum conformal Einstein field equations to give rise to a spaceti me development in possession of a Killing spinor. The fact that the confor mal Einstein field equations are used in our derivation allows for the pos sibility of the initial hypersurface intersecting non-trivially with (or e ven being a subset of) null infinity. For conciseness\, these conditions a re derived assuming that the initial hypersurface is spacelike. Hence\, in particular\, these conformal Killing spinor initial data equations encode necessary and sufficient conditions for the existence of a Killing spinor in the development of asymptotic initial data on spacelike components of null infinity.
END:VEVENT BEGIN:VEVENT SUMMARY:Applications of the Wigner function to quantum problems involving angle variables DTSTART:20220628T140000Z DTEND:20220628T160000Z DTSTAMP:20240329T082742Z UID:6734d4d6-9912-45a1-8c28-b64197bd4267 SEQUENCE:1 CREATED:20220627T080922Z DESCRIPTION:In this thesis the model of the Quantum Pendulum is studied in the Wigner function representation and in the Density Operator representa tion. Towards this end a completely solvable auxiliary model is introduced . Several families of solutions of the stationarity equations are found an d compared. The advantage of using the Wigner function in the discovery of these solutions is made evident. A simpler approach to the derivation of the evolution equations is developed. Links with Mathieu functions and the Helmholtz equation of classical mathematical-physics are analized. LAST-MODIFIED:20220627T080922Z LOCATION:Sala P12\, Piso 2\, Pavilhão Matemática\, Campus da Alameda URL:http://df.vps.tecnico.ulisboa.pt/eventos/applications-of-the-wigner-fu nction-to-quantum-problems-involving-angle-variables/ X-ALT-DESC;FMTTYPE=text/html:In this thesis the model of the Quantum Pendulum is studied in the Wigner function representa tion and in the Density Operator representation. Towards this end a comple tely solvable auxiliary model is introduced. Several families of solutions of the stationarity equations are found and compared. The advantage of us ing the Wigner function in the discovery of these solutions is made eviden t. A simpler approach to the derivation of the evolution equations is deve loped. Links with Mathieu functions and the Helmholtz equation of classica l mathematical-physics are analized.
END:VEVENT BEGIN:VEVENT SUMMARY:7ª MEFT Workshop DTSTART:20220629T090000Z DTEND:20220629T140000Z DTSTAMP:20240329T082742Z UID:76b4ff4a-6481-461d-bb07-95c128180f8d SEQUENCE:2 CREATED:20220626T153931Z DESCRIPTION:Convidamos a comunidade do Instituto Superior Técnico a parti cipar na 7ª Workshop dos alunos do mestrado de Engenharia Física Tecnol ógica. Neste encontro os alunos apresentam os projetos de investigação que vão fazer no âmbito Dissertação de Mestrado.O encontro vai decorre r na quarta-feira 29 Junho\, das 9h00 às 13h00 no Anfiteatro Abreu Faro. O programa da workshop encontra-se neste link.Esta workshop é parte integ rante da disciplina “Projeto Integrador de 2º Ciclo em Engenharia Físi ca Tecnológica” do curso de mestrado de engenharia Física Tecnológica .A Comissão Organizadora: alunos da disciplina “Projeto Integrador de 2 º Ciclo em Engenharia Física Tecnológica” LAST-MODIFIED:20220626T154414Z LOCATION:Anfiteatro Abreu Faro URL:http://df.vps.tecnico.ulisboa.pt/eventos/7%C2%AA-meft-workshop/ X-ALT-DESC;FMTTYPE=text/html:Convidamos a comuni
dade do Instituto Superior Técnico a participar na 7ª Workshop dos aluno
s do mestrado de Engenharia Física Tecnológica. Neste encontro os alunos
apresentam os projetos de investigação que vão fazer no âmbito Disser
tação de Mestrado.
O encontro vai deco
rrer na quarta-feira 29 Junho\, das 9h00 às 13h00 no Anfiteatro Abreu Far
o. O programa da workshop encontra-se neste link.
Esta worksho p é parte integrante da disciplina “Projeto Integrador de 2º Ciclo em Engenharia Física Tecnológica” do curso de mestrado de engenharia Fís ica Tecnológica.
A Comissão Organizado
ra: alunos da disciplina “Projeto Integrador de 2º Ciclo em Engenharia
Física Tecnológica”
Abstract
The AWAKE experime nt aims to accelerate leptons to the TeV regime. It will accomplish its go al with a highly energetic proton beam as a wakefield driver. However\, to increase the magnitude of the acceleration gradients produced by the driv er\, one must extend its propagation distance. Prolonging the current stag e would be experimentally challenging due to the self-consistent evolution of the ionisation front used during this stage.
We propose adding a pre-formed plasma stage\, to the existing sta
ge\, where the half-modulated beam (result of the first stage) can propaga
te. This work aims to study how the wake of the unmodulated part interacts
with the modulated part of the beam during the second stage. We first ana
lysed the impact of various wakefield parameters on the structure of the m
odulated beam\, and concluded that the wake'\;s phase is the most rele
vant parameter for the conservation of the beam. Next\, we analysed in det
ail the propagation of a partially modulated beam. The results showed that
seeding the modulation of the unmodulated part is the best approach to gu
arantee higher acceleration gradients during the second stage.
Lastly\, we demonstrated that we can adjust the len
gth of the simultaneously accelerating and focusing region of a wakefield
produced by two sources\, by controlling their width\, and the spacing bet
ween them. This is an important result that allows us to increase the acce
lerator'\;s efficiency\, by increasing the number of efficiently accel
erated particles.
Abstract:
We will discuss the shado w calculation of the loop quantum gravity motivated regular black hole rec ently proposed by Ashtekar\, Olmedo and Singh (AOS black hole hereafter). In the process\, we also construct the rotating loop quantum gravity inspi red solution of the originally proposed static spherically symmetric AOS b lack hole by applying the modified Newman-Janis algorithm. We study the qu antum effects on the shadows of both the non-rotating and rotating loop qu antum black hole solutions. It is observed that the general shape of the s hadow for nonrotating AOS black hole is circular in shape as is expected f or its classical counterpart too\, but the presence of loop quantum gravit y inspired modification contracts the shadow radius and the effect reduces with the increase in the mass of the black hole. On a similar note\, in t he rotating situation\, we find contraction in shadow radius due to quantu m effects and the tapered nature of the shadow as expected from the classi cal Kerr case. However\, instead of the symmetrical contraction\, like non -rotating one\, we found more contraction on one side relative to the othe r when we compare our result with the shadow of the Kerr black hole. We fi nally studied super-radiance in rotating AOS background and observed that the super-radiance condition for massless scalar field is identical to tha t of the Kerr case with the rotation of the BH being more compared to Kerr in the low mass regime. With an increase in mass of the rotating AOS blac k hole\, the difference from Kerr starts to become insignificant. We also perform the calculation of the super-radiance amplification factor using T eukolsky formalism in the AOS background and present a comparative study o f the amplification factors of the AOS and Kerr black holes with respect t o changing mass and spin of the holes.
END:VEVENT BEGIN:VEVENT SUMMARY:11º Encontro "LEFT | A desafiar os limites em ciência e tecnolog ia" DTSTART:20220701T090000Z DTEND:20220701T180000Z DTSTAMP:20240329T082742Z UID:d5fcbabe-44f3-40c7-a4e1-e3eea193a045 SEQUENCE:13 CREATED:20220609T091036Z DESCRIPTION:É um encontro destinado aos alunos do ensino secundário (e a vocês)\, para falarmos de uma forma descontraída e informal sobre a &qu ot\;Licenciatura em Engenharia Física e Tecnológica"\; no IST\, e fa z 10 anos que arrancámos com estes encontros com futuros candidatos à LE FT/MEFT.As manhãs são dedicadas a [muitas] micropalestras (máximo de 10 minutos cada)\, sobre [super]temas da atualidade em física\, aplicaçõe s\, percursos\, etc...A tarde de 6ªFeira (15h00–18h00) será dedicada às visitas aos laboratórios.1 de julho\, 6ªFeira\, 9h00–18h00\,2 de j ulho\, sábado\, 9h30–13h00.Os alunos e professores podem inscrever-se d iretamente na página do encontro.Mais informações na página do evento. LAST-MODIFIED:20220629T152018Z LOCATION:VA3 (Pavilhão de Engª Civil) URL:http://df.vps.tecnico.ulisboa.pt/eventos/11-encontro-left-a-desafiar-o s-limites-em-ci%C3%AAncia-e-tecnologia/ X-ALT-DESC;FMTTYPE=text/html:É um encontro dest
inado aos alunos do ensino secundário (e a vocês)\, para falarmos de uma
forma descontraída e informal sobre a "\;Licenciatura em Engenharia
Física e Tecnológica"\; no IST\, e faz 10 anos que arrancámos com e
stes encontros com futuros candidatos à LEFT/MEFT.
As manhãs s
ão dedicadas a [muitas] micropalestras (máximo de 10 minutos cada)\, sob
re [super]temas da atualidade em física\, aplicações\, percursos\, etc.
..
A tarde de 6ªFeira (15h00–18h00) será
dedicada às visitas aos laboratórios.
1 de julho\, 6ªFeira\, 9
h00–18h00\,
2 de julho\, sábado\, 9h30–1 3h00.
Os alunos e professores podem inscrever -se diretamente na página do encontro.
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END:VEVENT BEGIN:VEVENT SUMMARY:Neutrino masses and the origin of matter through leptogenesis DTSTART:20220704T150000Z DTEND:20220704T170000Z DTSTAMP:20240329T082742Z UID:4d5c9ce4-e0d4-4a95-8b6c-eebf9f6c72ee SEQUENCE:5 CREATED:20220701T152037Z DESCRIPTION:AbstractThe properties of particles and antiparticles are firm ly established in collider physics. They appear to be on the same footing in the Standard Model\, which naturally poses the question of why the obse rved Universe is composed nearly exclusively of matter\, in contrast to li ttle or no primordial antimatter.Despite its remarkable success in describ ing many of the inner workings of Nature at its most fundamental level\, t he Standard Model struggles to explain the existence of a biased Universe. A compelling possibility is that the baryon asymmetry of the Universe is generated dynamically\, a scenario that is known as baryogenesis\, which i mplies the non-conservation of the baryon number B. In the past thirty to forty years\, several mechanisms for baryogenesis have been put forth: gra nd unified theory baryogenesis\, electroweak baryogenesis\, Affleck-Dine m echanism\, spontaneous baryogenesis.Nonetheless\, the most compelling one is the mechanism of baryogenesis via leptogenesis\, first proposed by Fuku gita and Yanagida\, whose simplest and theoretically best motivated realiz ation is within the seesaw mechanism of neutrino masses.In this thesis\, w e discuss the mathematical implementation of leptogenesis in the context o f type-I seesaw mechanism. Additionally\, we consider the evolution of the baryonic asymmetry during the course of different temperature regimes\, d iscriminating between the unflavoured and flavoured treatment of leptogene sis. Lastly\, we take into consideration the importance of decoherence eff ects in transition regimes\, which leads us to opt for an alternative desc ription under the formalism of density matrix equations. LAST-MODIFIED:20220704T094204Z LOCATION:Sala QA1.2\, 1\, Torre Sul\, Campus da Alameda URL:http://df.vps.tecnico.ulisboa.pt/eventos/neutrino-masses-and-the-origi n-of-matter-through-leptogenesis/ X-ALT-DESC;FMTTYPE=text/html:Abstract
The properties of
particles and antiparticles are firmly established in collider physics. Th
ey appear to be on the same footing in the Standard Model\, which naturall
y poses the question of why the observed Universe is composed nearly exclu
sively of matter\, in contrast to little or no primordial antimatter.
Despite its remarkable success in describing many of the inner workin
gs of Nature at its most fundamental level\, the Standard Model struggles
to explain the existence of a biased Universe. A compelling possibility is
that the baryon asymmetry of the Universe is generated dynamically\, a sc
enario that is known as baryogenesis\, which implies the non-conservation
of the baryon number B. In the past thirty to forty years\, several mechan
isms for baryogenesis have been put forth: grand unified theory baryogenes
is\, electroweak baryogenesis\, Affleck-Dine mechanism\, spontaneous baryo
genesis.
Nonetheless\, the most compelli
ng one is the mechanism of baryogenesis via leptogenesis\, first proposed
by Fukugita and Yanagida\, whose simplest and theoretically best motivated
realization is within the seesaw mechanism of neutrino masses.
In this thesis\, we discuss the mathematical implem
entation of leptogenesis in the context of type-I seesaw mechanism. Additi
onally\, we consider the evolution of the baryonic asymmetry during the co
urse of different temperature regimes\, discriminating between the unflavo
ured and flavoured treatment of leptogenesis. Lastly\, we take into consid
eration the importance of decoherence effects in transition regimes\, whic
h leads us to opt for an alternative description under the formalism of de
nsity matrix equations.
Abstract
BepiColombo is the
first European mission to the Hermean system. It was launched in 2018 and
is predicted to enter Mercury’s orbit in late 2025. It is composed of t
wo spacecraft\, ESA'\;s Mercury Planetary Orbiter (MPO) and JAXA’s M
ercury Magnetospheric Orbiter (nicknamed Mio).
Among the instrume
nt suit of the MPO is the BepiColombo Radiation Monitor (BERM)\, that can
detect high energy protons (~1 to 200 MeV)\, electrons (~1 to 10 MeV) and
heavy ions. BERM is part of the spacecraft housekeeping\, with the objecti
ve of monitoring radiation hazards to prevent possible damage on the space
craft and instruments. Despite not being part of the scientific payload\,
its capability of measuring such high energies and its operational state d
uring all phases of the mission makes it an asset for scientific objective
s as well. BERM consists of a single stack with 11 Silicon detectors inter
leaved by aluminum and tantalum absorbers. BERM identifies particles type
and energies through the signals resultant from its interaction with the s
tack\, assigning each particle to one of 18 channels: five dedicated to el
ectrons\, eight to protons\, and five to heavy ions. The monitor provides
daily files with the number of registered counts in each channel integrate
d over 30 seconds sampling intervals. Obtaining particle fluxes from the B
ERM channel counts is not straightforward. In this work\, the bow-tie meth
od\, introduced by Van Allen in 1979\, was applied to convert flight count
rates to proton and electron fluxes. The results were used to analyze sol
ar events detected by BERM.
(Contactar Ana Bela Cardoso para pass
word) ana.bela.cardoso@tecnico.ulisboa.pt
Abstract
The interaction between p lasmas and magnetic obstacles often occur in astrophysical and space envir onments such as in ion-scale “mini magnetospheres”. Such systems displ ay a wide range of physical mechanisms and provide a unique environment fo r studying kinetic-scale plasma physics. In this work\, we present collisi onless particle-in-cell (PIC) simulations of ion-scale magnetospheres that reproduce recent laboratory experiments performed on the Large Plasma Dev ice (LAPD) at UCLA. In our PIC simulations\, a driver plasma flows against a dipolar magnetic field that is embedded in a uniform magnetized backgro und plasma. The simulations replicate the main magnetospheric structures o bserved in the experiments\, namely the magnetopause and the plasma curren t distributions. We show the formation of a magnetic cavity and a magnetic compression and two main current structures in the dayside region. From m ultiple parameter scans\, we show a reflection of the magnetic compression \, bounded by the length of the driver plasma\, and a higher separation of the main current structures for lower dipolar magnetic moments. Additiona lly\, we develop a analytical model that characterize the coupling between the driver and the magnetized background plasmas. The model is compared w ith the simulations\, showing good agreement.
(Contactar Ana Bela Cardoso para password) ana.bela.cardoso@tecnico.
ulisboa.pt
Abstract:
During this pr esentation\, I will describe the work I developed during the past ~1.5 yr in the scope of the Gaia-ESO survey\, which has recently been made complet ely public (Randich et al. 2022 A&\;A accepted\; Gilmore et al. 2022 A& amp\;A submitted). I will focus this presentation on a sample of old super metal-rich stars currently inhabiting the Solar vicinity analysed in Dant as et al. (2022a\, A&\;A in review). Several chemo-dynamic parameters ( along with their ages and super-metallicity) indicate that they have migra ted from the inner regions of the Milky Way\, including orbits of low ecce ntricity (e≲0.2)\, maximum height from the Galactic plane between ~0.5-1 .5 kpc\, and lack of radial metallicity gradient. These results are in acc ordance with several other works in the literature (e.g. Kordopatis et al. 2015) and predictions from simulations (e.g. Khorpeskov et al. 2020). I w ill end my presentation by showing an additional analysis of the effects o f radial migration on lithium abundances of these stars which will be subm itted in the shape of a letter (Dantas et al. 2022b\, A&\;A letters - t o be submitted).
END:VEVENT BEGIN:VEVENT SUMMARY:Higgs-Dilaton inflation in Einstein-Cartan gravity DTSTART:20220714T143000Z DTEND:20220714T163000Z DTSTAMP:20240329T082742Z UID:71e86497-8b5a-4a0b-9289-d1d14f7452f0 SEQUENCE:2 CREATED:20220712T084832Z DESCRIPTION:Abstract:Gravity can appear in different incarnations\, from t he commonly used metric formulation to the Palatini\, teleparallel and Ein stein-Cartan ones. Despite the difference in the choice of the fundamental degrees of freedom\, all these formulations are equivalent in pure gravit y scenarios\, leading to the same equations of motion\, therefore being de void of any observational consequence. However\, this equivalence is broke n in the presence of a non-minimal coupling to matter\, such as the Standa rd Model Higgs.Such coupling opens the possibility for the Higgs field to be responsible for the inflationary phase in the early universe. In this t alk\, I will discuss the phenomenology of Higgs-Inflation in the context o f Einstein-Cartan gravity\, together with its scale-invariant version\, th e so-called Higgs-Dilaton model. In particular\, I will show how the Einst ein-Cartan formulation can endow a rich phenomenology\, due to the unavoid able presence of extra gravitational operators\, and interactions with fer mionic matter. In a second part\, I will discuss how this scenario can acc ommodate the formation of scalar compact objects in the early universe and the possible emission of gravitational waves. LAST-MODIFIED:20220712T084851Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/higgs-dilaton-inflation-in-ei nstein-cartan-gravity/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
Gravity can appear in different incarnations\, from the commonly used me
tric formulation to the Palatini\, teleparallel and Einstein-Cartan ones.
Despite the difference in the choice of the fundamental degrees of freedom
\, all these formulations are equivalent in pure gravity scenarios\, leadi
ng to the same equations of motion\, therefore being devoid of any observa
tional consequence. However\, this equivalence is broken in the presence o
f a non-minimal coupling to matter\, such as the Standard Model Higgs.
Such coupling opens the possibility for the
Higgs field to be responsible for the inflationary phase in the early uni
verse. In this talk\, I will discuss the phenomenology of Higgs-Inflation
in the context of Einstein-Cartan gravity\, together with its scale-invari
ant version\, the so-called Higgs-Dilaton model.
In particular\,
I will show how the Einstein-Cartan formulation can endow a rich phenomen
ology\, due to the unavoidable presence of extra gravitational operators\,
and interactions with fermionic matter. In a second part\, I will discuss
how this scenario can accommodate the formation of scalar compact objects
in the early universe and the possible emission of gravitational waves.
p>
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dynamics LFS and HFS density profiles at ASDEX Upgrade - Effect of
magnetic configuration and divertor conditions
DTSTART:20220718T140000Z
DTEND:20220718T160000Z
DTSTAMP:20240329T082742Z
UID:2207955a-b5f3-4137-ad02-4a5aaa0a9472
SEQUENCE:1
CREATED:20220715T091501Z
DESCRIPTION:Abstract:Future fusion devices\, including ITER\, will need to
operate with a detached divertor regime. Divertor detachment is often lin
ked to the formation of a high-density front on the high-field side (HFS)
that significantly influences the profiles at the inboard midplane. HFS pr
ofiles are also remarkably sensitive to the magnetic configuration and\, i
n particular\, to the connection between the LFS and the HFS. The physics
behind these observations is not yet fully understood as experimental data
from the HFS is often scarce. The O-mode reflectometer at ASDEX Upgrade i
s a valuable tool as it allows measuring the density profiles both on the
LFS and HFS. In this work\, we investigate the influence of ballooning tra
nsport and the high-density front in establishing HFS density profiles usi
ng as main experimental tolls scans in the magnetic configuration and in t
he divertor conditions. Our observations have shown that the high-density
region is limited to the flux surface containing the secondary X-point and
leads to inverted density gradients very close to the inner separatrix.
LAST-MODIFIED:20220715T091501Z
LOCATION:Online
URL:http://df.vps.tecnico.ulisboa.pt/eventos/dynamics-lfs-and-hfs-density-
profiles-at-asdex-upgrade-effect-of-magnetic-configuration-and-divertor-co
nditions/
X-ALT-DESC;FMTTYPE=text/html:
Abstract:
Future fusion devices\, including ITER\, will need to operate with a det
ached divertor regime. Divertor detachment is often linked to the formatio
n of a high-density front on the high-field side (HFS) that significantly
influences the profiles at the inboard midplane. HFS profiles are also rem
arkably sensitive to the magnetic configuration and\, in particular\, to t
he connection between the LFS and the HFS. The physics behind these observ
ations is not yet fully understood as experimental data from the HFS is of
ten scarce.
The O-mode reflectometer at
ASDEX Upgrade is a valuable tool as it allows measuring the density profi
les both on the LFS and HFS. In this work\, we investigate the influence o
f ballooning transport and the high-density front in establishing HFS dens
ity profiles using as main experimental tolls scans in the magnetic config
uration and in the divertor conditions. Our observations have shown that t
he high-density region is limited to the flux surface containing the secon
dary X-point and leads to inverted density gradients very close to the inn
er separatrix.
É com enorme praze r que convidamos toda a comunidade para a cerimónia de atribuição do t ítulo de Professor Emérito aos Professores Gustavo Castelo-Branco e Jo rge Romão e do título de Investigador Emérito ao Dr. Emílio Ribeiro.
O títu lo de Investigador e Professor Emérito é conferido pela Universidade de Lisboa aos Investigadores e Professores já aposentados\, reformados ou ju bilados\, que atingiram alto grau de projecção no exercício da sua ativ idade académica\, que se destacaram na sua área de especialidade\, pela relevância e/ou magnitude da sua produção e atividade científicas\, desfrutando de grande reconhecimento pela comunidade académica.
O Departamento de F ísica está a organizar uma Cerimónia de atribuição de Grau\, a aconte cer no dia 19/07 pelas 16h00\, no Centro de Congressos do IST\, a qual con tará com a presença do Sr. Reitor da Universidade de Lisboa\, do Preside nte do IST e do Presidente do DF\, anfitrião da cerimónia.
Esperamos ver-vos a tod os nesta cerimónia de homenagem a colegas que contribuiram para tornar o DF uma referência internacional.
END:VEVENT BEGIN:VEVENT SUMMARY:Exotic Higgs bosons at the LHC DTSTART:20220720T143000Z DTEND:20220720T163000Z DTSTAMP:20240329T082742Z UID:065559e5-3229-4eab-80e9-69e82f567ce3 SEQUENCE:1 CREATED:20220713T140945Z DESCRIPTION: Abstract:Any additional SM-like neutral Higgs boson is expect ed to be heavy as it would incur extremely tight constraints from electrow eak precision tests as well as from its non-observation at the LHC. A clas s of flavor models exists which predicts exotic neutral Higgses which\, un like the SM Higgs boson\, do not have couplings to VV pair (V = W\,Z)\, an d their Yukawa couplings are purely flavor off-diagonal (tc\, tu\, bs\, bd \, ... type\, without having any uu\, tt\, bb\, ... type diagonal coupling s). By virtue of these two properties they can bypass the stringent constr aints mentioned above\, provided the off-diagonal Yukawa couplings are not too large to attract some other constraints. Such exotic states can be li ght. The sizes of those flavor off-diagonal Yukawas are generally fixed by the requirement of correct reproduction of the quark masses and mixing in specific flavor models. But in this talk I shall take a model independent approach -- simply assume the presence of one such scalar and a pseudo-sc alar - both light - having off-diagonal Yukawa couplings whose sizes are r estricted by flavor observables\, and focus on how to dig out those states from the LHC data. LAST-MODIFIED:20220713T140945Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/exotic-higgs-bosons-at-the-lh c/ X-ALT-DESC;FMTTYPE=text/html:
Abstract:
Any additional SM-like neutral Higgs boso
n is expected to be heavy as it would incur extremely tight constraints fr
om electroweak precision tests as well as from its non-observation at the
LHC. A class of flavor models exists which predicts exotic neutral Higgses
which\, unlike the SM Higgs boson\, do not have couplings to VV pair (V =
W\,Z)\, and their Yukawa couplings are purely flavor off-diagonal (tc\, t
u\, bs\, bd\, ... type\, without having any uu\, tt\, bb\, ... type diagon
al couplings).
By virtue of these two p
roperties they can bypass the stringent constraints mentioned above\, prov
ided the off-diagonal Yukawa couplings are not too large to attract some o
ther constraints. Such exotic states can be light. The sizes of those flav
or off-diagonal Yukawas are generally fixed by the requirement of correct
reproduction of the quark masses and mixing in specific flavor models.
But in this talk I shall take a model inde
pendent approach -- simply assume the presence of one such scalar and a ps
eudo-scalar - both light - having off-diagonal Yukawa couplings whose size
s are restricted by flavor observables\, and focus on how to dig out those
states from the LHC data.
Abstract p>
Light can carry and transfer a well-defined or bital angular momentum (OAM) [1] along the propagation axis and is often c alled twisted light. This quality opens new research in highly non-linear (I 1022 W/cm2) laser-plasma interactions\, including magnetic field gen eration [2]\, electron/positron acceleration in laser-plasma accelerators [3]\, high orbital angular momentum harmonic generation [4]\, and direct l aser acceleration of ions [5]. However\, the full potential of twisted lig ht interacting with plasma is yet unexplored.
We studied three novel scenarios analytically and through three-dim
ensional particle-in-cell simulations using OSIRIS [6]\; enhanced proton a
cceleration\, the light properties in the cutoff region of plasma\, and wa
kefield acceleration through light with self-torque.
The main project focused on proton acceleration. By exploiti
ng the benefits of a high-intensity twisted light pulse impinging a double
-layer target\, we could reduce the accelerated proton bunch divergence by
almost an order of magnitude while maintaining its energy compared to the
conventional Gaussian method [7]. Here\, we identified that relativistic
self-focusing in the near-critical plasma layer of the target and the ligh
t'\;s OAM contents play a crucial role in improved proton acceleration
.
We also explored light springs and li
ght with self-torque by combining twisted light modes. First\, a study of
the properties of a light spring in the cutoff region of plasma has shown
a similar characteristic behavior as a compressed mechanical spring [8]. S
econd\, we identified that a wakefield configuration with self-torque in t
he non-linear regime leads to azimuthal forces and the formation of quasi-
helical electron beams [9].
Twisted lig
ht is still an open field in laser-plasma research and has the potential t
o lead to new regimes of particle acceleration\, radiation processes\, and
eventually laser fusion research.
Abstract: p>
Compact stars due to their enormous gravitatio nal field can accumulate a sizable amount of dark matter in their interior . Depending on its nature\, an accumulated dark matter may affect the prop erties of neutron stars in quite different ways. I will give an overview o f the impact of dark matter on various observable properties of neutron st ars\, i.e. the mass-radius relation\, tidal deformability\, surface temper ature\, merger dynamics and gravitational wave waveform\, etc.
For two scenarios\, asymmetric fermionic and boson
ic dark matter\, the conditions at which dark matter particles tend to con
densate in the core of the star or create an extended halo will be present
ed. I will show how dark matter condensed in a core tends to decrease the
total gravitational mass and tidal deformability compared to a pure baryon
ic star\, which appears as an effective softening of the equation of state
. On the other hand\, the presence of a dark matter halo has an opposite e
ffect\, causing an increase of those observable quantities. Thus\, observa
tional data on compact stars could be affected by an accumulated dark matt
er and\, consequently\, constraints we put on the strongly interacting mat
ter at high densities. I will discuss how the ongoing and future X-ray\, r
adio and gravitational wave observations could shed light on dark matter a
dmixed compact stars and put multi-messenger constraints on thecorrespondi
ng effect.
Abstract:Quantum computers can solve various problems more efficiently than clas sical computers. While there are still no large-scale quantum computers\, one can study the complexity of quantum algorithms and understand which on es have a theoretical advantage over their classical counterparts. In this presentation\, I propose new quantum algorithms for the object reconstruc tion problems of tracking and clustering\, which occur frequently in the c ontext of particle physics data analysis. The goal of these problems is to group the data points according to some specified geometrical rule. Using amplitude amplification routines\, I show that a polynomial quantum speed up is reachable assuming coherent access to the classical input data. I wi ll finish the presentation by mentioning undergoing work on other object r econstruction problems\, both in fault-tolerant and restricted-depth setti ngs.
END:VEVENT BEGIN:VEVENT SUMMARY:The Future Circular Collider: Recent development in physics and de tector studies DTSTART:20220906T143000Z DTEND:20220906T163000Z DTSTAMP:20240329T082742Z UID:5f2b8c8d-2379-4be5-87ce-ad0a7a6521e4 SEQUENCE:1 CREATED:20220905T104517Z DESCRIPTION: Abstract:Along the path defined by The European Strategy for Particle Physics\, a financial and technical feasibility study of the FC C colliders and their infrastructure has been carried out for the next upg rade of the strategy around 2025/6. The FCC program combines in the same 1 00km infrastructure a high luminosity Higgs and Electroweak factory e+e- c ollider\, FCC-ee\, followed by a 100 TeV hadron collider. The main challen ges of the current effort are both about physics potential and performance studies and for detector design to fully exploit its potential\, while be ing technically feasible and affordable on the project time scale (start o f operations around 2040). The most striking detector challenges will be h ighlighted\, then focusing on the IDEA experiment proposed for the FCC-ee by the INFN Italian community. While providing a global view of the IDEA s ubdetectors and the new technologies used \, more details will be given ab out the project of an ultra-low mass Drift Chamber as the central tracking system of IDEA. LAST-MODIFIED:20220905T104517Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/the-future-circular-collider- recent-development-in-physics-and-detector-studies/ X-ALT-DESC;FMTTYPE=text/html:
Abstract:
Along the path defined
by The European Strategy for Particle Physics\, a financial and technica
l feasibility study of the FCC colliders and their infrastructure has been
carried out for the next upgrade of the strategy around 2025/6. The FCC p
rogram combines in the same 100km infrastructure a high luminosity Higgs a
nd Electroweak factory e+e- collider\, FCC-ee\, followed by a 100 TeV hadr
on collider.
The main challenges of the current effort are both
about physics potential and performance studies and for detector design to
fully exploit its potential\, while being technically feasible and afford
able on the project time scale (start of operations around 2040).
The most striking detector challenges will be highlighted\, then focusin
g on the IDEA experiment proposed for the FCC-ee by the INFN Italian commu
nity. While providing a global view of the IDEA subdetectors and the new t
echnologies used \, more details will be given about the project of an ult
ra-low mass Drift Chamber as the central tracking system of IDEA.
Abstract:
The ESTHER shock tube is a new state-of-the-art facili
ty at Instituto Superior Técnico to support future ESA planetary explorat
ion missions. The facility recreates the re-entry plasma conditions sustai
ned by a hypersonic velocity atmospheric entry.
These shock wave
velocities are in the range of 4 to 14 km/s range. A high-pressure combus
tion chamber using a mixture of He:H2:O2 ignited by a high-power Nd:YAG la
ser acts as the driver. A qualification campaign was carried out with 100
shots and evaluating the effects of air:fuel ratio\, filling pressure\, in
ert gas dilution and ignition mode. These parameters directly affect the p
roduced shockwave velocity and should be effectively controlled.
Alongside the driver qualification the development of different diagnostic
s is presented\, namely the VUV spectroscopy system and a compact reflecto
meter/interferometer for space applications. Technical requirements and ar
chitecture of a reflectometry/interferometry equipment tailored for both g
round-test facilities (shock-tubes and plasma wind-tunnels) and flight exp
eriments are proposed.
A simulation of e
lectromagnetic environment for the RAM-C flight experiment\, obtained usin
g a CFD code coupled to an electromagnetic propagation code is presented\,
outlining the adequacy of such a diagnostic for improving verification an
d validation for high-speed entry plasma flows.
Abstract:
In t
his talk I review some bounds on light dark matter\, derived from astrophy
sical observables. I focus on axion and axion-like particles\, as well as
on dark photons. I present constraints on these particles from MS stars\,
Globular Clusters and compact objects\, and some recent results about dark
photons obtained by my collaborators and me. In addition\, I discuss a fu
ture work on the Lyman-alpha forest\, in order to elucidatethe role of axi
ons as dark matter candidates.
Abstract:
Most galaxies in the univ
erse spend their lives inhabiting what is called the main-sequence (MS) of
star-formation\, a peaceful and gentle state in which galaxies form stars
and feed their central massive black holes (BHs) in a steady manner.
However\, simulations and observations suggest that\, at least once i
n their life-times\, galaxies undergo a merger event during which their st
ar formation efficiencies and BH accretion rates drastically increase over
a short period of time.
This phase in galaxy evolution occurs be
hind a thick blanket of dust and gas that obscures the central\, very lumi
nous power source(s). The study of this incredibly luminous galaxy populat
ion is therefore fundamental to our understanding of the main physical pro
cesses that drive the evolution of galaxies over cosmic time.
In
this talk I will present results obtained from infrared observations of ne
arby and high-redshift luminous infrared galaxies\, for which in-depth stu
dies of their interstellar medium have been only recently made possible by
the advent of state-of-the-art telescope facilities such as Herschel\, AL
MA\, and now JWST.
Abstract:
In this talk\, I will review the contribution of solar neutrinos to our currently well-established three-neutrino oscillation pi cture and the prospects for the study of neutrino properties beyond masses and mixing. Firstly\, I will discuss how next-generation experiments JUNO and Hyper-Kamiokande will provide strong constraints on non-standard inte ractions while determining the oscillation parameters with unprecedented p recision. Then\, I will also show how\, in the case of Majorana neutrinos\ , the non-observation of a solar antineutrino flux can set limits on neutr ino magnetic moments. Finally\, I will briefly review other constraints on neutrino properties from solar neutrinos.
END:VEVENT BEGIN:VEVENT SUMMARY:Unconventional ways to measure the Hubble constant with lensed and non-lensed supernovae DTSTART:20220922T143000Z DTEND:20220922T163000Z DTSTAMP:20240329T082742Z UID:db616dfb-149c-4a3e-9225-b2b28bce141a SEQUENCE:1 CREATED:20220916T120035Z DESCRIPTION: Abstract:The precise determination of the Hubble constant ha s gained enormous attention after a discrepancy between local and early-un iverse measurements has become evident with the release of the first data from the Planck satellite almost 10 years ago. Since then\, this discrepan cy\, known as the "\;Hubble tension"\;\, has grown to more than 5 sigma\, and may hint at new physics beyond the LambdaCDM standard model of cosmology. I will present two projects that aim to use supernovae to meas ure the Hubble constant in the local universe. Both methods provide stand- alone one-step measurements that are completely independent of the distanc e ladder. In the first approach\, the "\;adH0cc"\; collaboration a ugments the classical expanding-photosphere method with tailored spectral modelling to determine distances of Type II supernovae. The method is appl ied to spectral time series of supernovae in the Hubble flow obtained thro ugh a dedicated ESO Large Programme. In the second approach\, the "\;H OLISMOKES"\; team aims to use supernovae that are strongly lensed and multiply imaged by a massive foreground galaxy. By measuring the temporal delays between their multiple images\, the so-called time-delay distance a nd hence the Hubble constant can be inferred. From both programmes we expe ct measurements with 5% precision within the next years. LAST-MODIFIED:20220916T120035Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/unconventional-ways-to-measur e-the-hubble-constant-with-lensed-and-non-lensed-supernovae/ X-ALT-DESC;FMTTYPE=text/html:
Abstract:
The precise determinat
ion of the Hubble constant has gained enormous attention after a discrepan
cy between local and early-universe measurements has become evident with t
he release of the first data from the Planck satellite almost 10 years ago
.
Since then\, this discrepancy\, known as the "\;Hubble ten
sion"\;\, has grown to more than 5 sigma\, and may hint at new physics
beyond the LambdaCDM standard model of cosmology. I will present two proj
ects that aim to use supernovae to measure the Hubble constant in the loca
l universe. Both methods provide stand-alone one-step measurements that ar
e completely independent of the distance ladder. In the first approach\, t
he "\;adH0cc"\; collaboration augments the classical expanding-pho
tosphere method with tailored spectral modelling to determine distances of
Type II supernovae.
The method is applied to spectral time seri
es of supernovae in the Hubble flow obtained through a dedicated ESO Large
Programme. In the second approach\, the "\;HOLISMOKES"\; team aim
s to use supernovae that are strongly lensed and multiply imaged by a mass
ive foreground galaxy. By measuring the temporal delays between their mult
iple images\, the so-called time-delay distance and hence the Hubble const
ant can be inferred. From both programmes we expect measurements with 5% p
recision within the next years.
Computational and analytical models predict several mechanisms
of transport of angular momentum (AM) and of mixing of chemical elements c
apable of describing some of the physical phenomena in star’s interiors
through their evolution. Nonetheless\, recent measurements of core rotatio
n rates of red giants enabled by the Kepler mission\, indicating a possibl
e missing AM transfer mechanism in the current theory of stellar interiors
.
In the first part of this work\,
we use the Modules for Experiments in Stellar Astrophysics (MESA) stellare
volution code to compute models of low mass rotating stars from the zero-a
ge main sequence (ZAMS) to the red giant branch (RGB) calibrating them to
a specific Kepler asteroseismic target\, KIC8579095.
We include transport of AM and rotation-induced chemical
mixing due to magnetic fields in radiative zones\, using the Tayler-Sprui
t dynamo formalism and the recent revision by Fuller et al. (2019) (named
Fuller-formalism)\, which has showed very promising results for red giant
models. We also make use of the adiabatic pulsation code\, GYRE\, to furth
er study this mechanisms using asteroseismic observables. We find that onl
y the models including the Fuller prescription for AM transport were able
to predict the observed core rotation rates on the RGB. The efficiency of
transport of AM increases with inclusion of mixing\, predicting lower rota
tion rates in the RGB\, despite the mixing induced by the Fuller-formalism
being extremely small as expected.
In the second part\, we tested the efficiency of AM transport of Fuller-f
ormalism models with different input physics: stellar mass\, metallicity\,
convective overshooting and the free parameter of this theory. We found m
odels particularly sensible to variations in initial mass\, but less to me
tallicity and overshooting. Lastly\, using a sample of 1093 stars with mas
ses in the 1-2 solar mass range that include all the stellar evolution pha
ses from main-sequence (MS) up to the red clump (RC)\, we study the transf
er of AM through these phases. To that end\, we modeled a typical star wit
h a mass of 1.5 M and compared the results obtained with asteroseismic obs
ervations for this group of stars. We found that a wider range for the α
parameter [0.5\;5] in the Fuller-formalism is needed to reproduce the part
icular measurements of RGB and RC stars.
Abstract:
General relativity can describe various gravitational
systems of astrophysical relevance\, like black holes and neutron stars\,
or even strongly coupled systems through the holographic duality. In addit
ion\, more formal aspects of the theory like the stability of spacetimes a
nd the formation of singularities are still topics of active research. In
several cases\, solutions in closed analytic form are not known\, and pert
urbative methods are inadequate\, leading to the employment of numerical t
echniques.
The characteristic initial (boundary) value problem h
as numerous applications in general relativity involving numerical studies
and is often formulated using Bondi-like coordinates. Well-posedness of t
he resulting systems of partial differential equations\, however\, remains
an open question. The answer to this question affects the accuracy\, and
potentially the reliability of conclusions drawn from numerical studies ba
sed on such formulations.
A numerical approximation can converge
to the continuum limit only for well-posed systems. The notion of well-po
sedness is tightly related to that of hyperbolicity and includes the speci
fication of a norm. In the first part of this thesis\, we expand our under
standing of the hyperbolicity and well-posedness of Bondi-like free evolut
ion systems. We show that several prototype Bondi-like formulations are on
ly weakly hyperbolic and examine the root cause of this result. In a linea
r analysis we identify the gauge\, constraint and physical blocks in the p
rincipal part of the Einstein field equations in such a gauge\, and we sho
w that the subsystem related to the gauge variables is only weakly hyperbo
lic. Weak hyperbolicity of the full system follows as a consequence in man
y cases.
We demonstrate this explicitly in specific examples\, a
nd thus argue that Bondi-like gauges result in weakly hyperbolic free evol
ution systems under quite general conditions. Consequently\, the character
istic initial (boundary) value problem of general relativity in these gaug
es is rendered ill-posed in the simplest norms one would like to employ. W
e discuss the implications of this result in accurate gravitational wavefo
rm modeling methods and work towards the construction of alternative norms
that might be more appropriate.
We also present numerical tests
that demonstrate weak hyperbolicity in practice and highlight important f
eatures to perform them effectively. In the second part\, we turn our atte
ntion to applications of these formulations to strongly coupled systems vi
a holography. We expect these studies to shed more light on the qualitativ
e behavior of strongly coupled plasmas\, but due to weak hyperbolicity\, w
e cannot perform rigorous error estimates to our satisfaction. We present
Jecco\, a newly developed characteristic code that allows us to simulate t
he dynamics of strongly coupled plasmas.
Representative examples
of the simulations that can be achieved with this code are provided\, nam
ely the out-of-equilibrium dynamics of said plasmas that undergo phase tra
nsitions. This is a putative scenario of the early universe and such simul
ations might provide insights into questions of fundamental nature.
Abstract:
The
main focus of the research is to check for possible Higgs-like dark matter
candidates within three-Higgs-doublet models with an underlying S3 symmet
ry. In our framework the stability of the dark matter sector results from
a Z2 symmetry which survives the breaking of S3.
We catalogue al
l possible dark matter models within this framework. Furthermore\, two mod
els (with and without CP violation in the Higgs potential) are explored ba
sed on theoretical and experimental constraints.
After applying
a number of successive checks over the parameter space we found different
viable dark matter mass regions within the range of [6\, 90] GeV depending
on the model. Further work is under way along these lines.
Abstract:
The Robinson-Trautman (RT) spacetime is the simplest solution of General
Relativity (GR) describing a compact source surrounded by gravitational w
aves. As an initial value problem\, the RT spacetime evolution is a well-p
osed mathematical problem. The pertinent dynamical equations are equivalen
t to the so-called Calabi flow\, and regular initial data evolve smoothly
towards a final state corresponding to a remnant Schwarzschild black hole.
Extensions of RT spacetimes for higher dimensions (D >\; 4) w
ere recently proposed\, and the essence of the RT evolution is unchanged:
regular initial data evolve towards a final higher-dimensional Schwarzschi
ld black hole. The situation for D=3 is quite different due to some peculi
arities of low-dimensional GR. We will present a D=3 RT flow mimicking the
essential properties of the Calabi flow. In particular\, regular initial
data evolve towards a final remnant BTZ black hole\, and any possible asym
metry in the initial data is expelled as a radiation fluid.
Abstract:
Microscopic gravitational systems involving blac
k holes and matter present quantum and thermodynamic properties that are w
orth of study.
Due to the breaking
of the vacuum from a strong gravitational field near the event horizon of
a black hole\, particles\, such as gravitons or other matter fields\, are
emitted to infinity with a definite temperature\, the Hawking temperature.
Left by itself\, a black hole loses mass in this emission process until i
t eventually disappears.
To underst
and more deeply the connection and conversion between black holes and hot
matter fields\, one has thus to enclose the black hole and the hot matter
inside a heat reservoir which is maintained at constant temperature and co
nstant radius\, and which in turn characterizes the canonical ensemble of
statistical mechanics. A thermodynamic treatment for the system black hole
plus hot matter is then possible. We model the hot matter fields by a hot
thin shell that surrounds a black hole and is inside the heat reservoir.<
br/>
To work out the quantum partition f
unction\, from which the thermodynamics of the system emerges\, we use the
Euclidean path integral approach to quantum gravity that identifies the p
ath integral of the gravitational system with the partition function itsel
f. In a zeroth order\, semiclassical\, evaluation of the path integral\, o
ne computes the Euclidean classical action of the system which\, at this o
rder\, is equal to the system'\;s thermodynamic free energy divided by
the temperature. Several important consequences related to the energy\, t
he temperature stratification\, the entropy\, and the thermodynamic stabil
ity of the system unfold in a natural way.
A most significant result is the finding of the various possible th ermodynamic phases of the ensemble\, specifically\, pure black hole spaces \, pure hot shell spaces\, hot shell with a black hole spaces\, and hot fl at spaces\, and the establishing of the possible phase transitions between them through the identification of the ground state phase of the ensemble once a temperature equation of state for the matter in the hot shell is g iven. Yet another result connected with the conversion of pure black holes into curved spaces with hot matter in the form of hot thin shells and vic e versa\, is that the systems in some instances perform as black hole ther modynamic mimickers and in another instance act as authentic dynamic and g eometric mimickers. The precise setting and all these results will be expl ained in some detail along the seminar.
END:VEVENT BEGIN:VEVENT SUMMARY:Quantum correlations: from quantum mechanical foundations to appli cations DTSTART:20221012T143000Z DTEND:20221012T163000Z DTSTAMP:20240329T082742Z UID:5d613d73-cdc4-430e-a8f9-b2fad21b07a3 SEQUENCE:2 CREATED:20221003T144159Z DESCRIPTION:Abstract:In this talk\, I will introduce quantum correlations\ , one of the key aspects of quantum information theory\, starting with the seminal example of Bell nonlocality. I will review Bell’s theorem\, whi ch shows how quantum mechanics cannot be simulated classically.Generalizat ions of Bell nonlocality and other types of quantum correlations will be o utlined. Experimental research and applications of quantum correlations wi ll be briefly discussed\, with a focus on quantum communication using quan tum optics and light-matter interaction. LAST-MODIFIED:20221003T144218Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/quantum-correlations-from-qua ntum-mechanical-foundations-to-applications/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
In this talk\, I will introduce quantum correlations\, one of the key as
pects of quantum information theory\, starting with the seminal example of
Bell nonlocality. I will review Bell’s theorem\, which shows how quantu
m mechanics cannot be simulated classically.
Generalizations of B
ell nonlocality and other types of quantum correlations will be outlined.
Experimental research and applications of quantum correlations will be bri
efly discussed\, with a focus on quantum communication using quantum optic
s and light-matter interaction.
Abstract:
Much effort has bee n invested during the last decades with the aim to develop a theory for di ssipative fluids in the context of General Relativity. One of the difficul ties that appear to that end is the parabolic nature of heat propagation\, which seems to go against the causality principle imposed by Einstein 7\;s theory. This problem makes the issue of modelling relativistic viscou s fluids a highly non-trivial task.
In t
his talk we shall review previous and current attempts at dissipative flui
d theories. After recalling the necessary conditions for a general hydrody
namic theory to be well-posed\, stable and causal\, we shall point out som
e issues that appear when studying the corresponding initial-value formula
tion and finally comment on future challenges and open problems\, both fro
m the analytic and numerical perspectives.
O DF vai dar as b oas vindas aos novos alunos do LEFT e MEFT\, dia 14 de Outubro. A recepç ão vai incluir uma descrição do departamento e dos eventos mais extrao rdinários dos últimos anos. Durante este evento\, vamos ouvir ex-alunos do DF\, incluindo Frederico Fiúza (actualmente Group Leader no SLAC\, S tanford)\, e alunos actuais como o Rafael Almeida. Vamos convidar o NFIST a mostrar-se e as novas caras do DF a apresentarem-se. E temos uma surpr esa para todos.
END:VEVENT BEGIN:VEVENT SUMMARY:Primordial Black Holes as laboratories for Physics beyond the stan dard scenarios DTSTART:20221018T143000Z DTEND:20221018T163000Z DTSTAMP:20240329T082742Z UID:c6a5f966-f224-43ce-bece-ff25667a87ba SEQUENCE:3 CREATED:20221014T131713Z DESCRIPTION:Abstract:We use the evaporation of primordial black holes (PBH s)\, of mass between 10^8 -10^12 kg\, as a laboratory to investigate Physi cs beyond the Standard Model of particles and to probe the structure of bl ack holes.We show that PBHs develop non-negligible spins through Hawking x27\;s emission of a large number of axion-like particles generically pres ent in string theory compactifications. This is because scalars can be emi tted in the monopole mode (l = 0)\, where no angular momentum is removed f rom the BH\, so a sufficiently large number of scalars can compensate for the spin-down produced by fermion\, gauge boson\, and graviton emission. T his yields a unique probe of the total number of light scalars in the fund amental theory\, independent of how weakly they interact with known matter .We propose a method to determine the mass and spin of PBHs based on measu ring the energy of specific features in the photon Hawking emission spectr um\, including both primary and secondary components. Since the proposed m ethod relies on the energy of the photons emitted by a given PBH\, rather than on the associated flux\, it is independent of the PBH-Earth distance and\, as a byproduct\, can also be used to infer the latter.We study a reg ular rotating black hole\, described by the Kerr-black-bounce metric\, eva porating under the Hawking emission of a single scalar field. We compare t he results with a Kerr black hole evaporating under the same conditions. T he Gray-body factors\, the asymptotic final spin\, the surface gravity\, a nd as a consequence temperature\, primary emissivity\, and lifetime\, are affected by the regularizing parameter. We briefly comment on the possibil ity of investigating the beyond-the-horizon structure of a black hole expl oiting its Hawking emission. LAST-MODIFIED:20221014T131808Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/primordial-black-holes-as-lab oratories-for-physics-beyond-the-standard-scenarios/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
We use the evaporation of primordial black hole
s (PBHs)\, of mass between 10^8 -10^12 kg\, as a laboratory to investigate
Physics beyond the Standard Model of particles and to probe the structure
of black holes.
We show that PBHs
develop non-negligible spins through Hawking'\;s emission of a large n
umber of axion-like particles generically present in string theory compact
ifications. This is because scalars can be emitted in the monopole mode (l
= 0)\, where no angular momentum is removed from the BH\, so a sufficient
ly large number of scalars can compensate for the spin-down produced by fe
rmion\, gauge boson\, and graviton emission. This yields a unique probe of
the total number of light scalars in the fundamental theory\, independent
of how weakly they interact with known matter.
We propose a method to determine the mass and spin of PBHs bas
ed on measuring the energy of specific features in the photon Hawking emis
sion spectrum\, including both primary and secondary components. Since the
proposed method relies on the energy of the photons emitted by a given PB
H\, rather than on the associated flux\, it is independent of the PBH-Eart
h distance and\, as a byproduct\, can also be used to infer the latter.
We study a regular rotating black hol
e\, described by the Kerr-black-bounce metric\, evaporating under the Hawk
ing emission of a single scalar field. We compare the results with a Kerr
black hole evaporating under the same conditions.
The Gray-body
factors\, the asymptotic final spin\, the surface gravity\, and as a conse
quence temperature\, primary emissivity\, and lifetime\, are affected by t
he regularizing parameter. We briefly comment on the possibility of invest
igating the beyond-the-horizon structure of a black hole exploiting its Ha
wking emission.
ABSTRACT: < /p>
We present an updated analysis of the first-o
rder phase transition associated with symmetry breaking in the early Unive
rse in a classically scale-invariant model extended with a new SU(2) gauge
group. Including recent developments in understanding supercooled phase t
ransitions\, we compute all of its characteristics and significantly const
rain the parameter space.
We then predict gravitational-wave spe
ctra generated during this phase transition and by computing the signal-to
-noise ratio we conclude that this model is well testable (and falsifiable
) with LISA. We also provide predictions for the relic dark matter abundan
ce. It is consistent with observations in a rather narrow part of the para
meter space\, as we exclude the so-called supercool dark matter scenario b
ased on an improved description of percolation and reheating after the pha
se transition as well as inclusion of the running of couplings.
Finally\, we pay special attention to renormalisation-scale dependence of
the results and even though our main results are obtained with the use of
renormalisation-group improved effective potential\, we also present the o
utcome of a fixed-scale analysis. It proves that the dependence on the sca
le is not only qualitative but also quantitative.
Abstract:
In r
ecently published works aiming to study the paramagnetic properties of mag
netic ionic liquids using 1H NMR relaxometry and diffusometry\, X-ray diff
ractometry revealed\, for some of the studied systems\, a well-defined loc
al structure motivated by the segregation of the polar and non-polar domai
ns [1]. Although these compounds did not present the same degree of order
as a liquid crystal\, it was only possible to consistently combine the dat
a from all experimental techniques considering order parameter fluctuation
s as a possible relaxation pathway.
The present work combines 1H
NMR relaxometry and diffusometry with X-ray scattering experiments in the
study of the molecular dynamics of magnetic and non-magnetic ionic liquids
based on the [P6\,6\,6\,14]+ and [C8mim]+ cations. The data from all expe
rimental techniques corroborated the need to consider either order paramet
er fluctuations or layer undulations in the model fitting analysis of thes
e ionic systems\, despite their apparent isotropic nature.
ABSTRACT: < /p>
Gravitational waves bring us rich insights in to the astrophysics of black holes and neutron stars. Detecting and interp reting these signals has been the culmination of decades of work on precis ion interferometry\, mathematical general relativity\, numerical relativit y\, signal modelling\, and data processing. I will focus on numerical rela tivity and waveform modelling\, with a summary of the field’s history\, the most recent advances\, and how and what they have taught us about the universe – and what is still to come. Finally\, I will discuss one of th e latest results\, the first measurement of strong-field general-relativis tic precession.
END:VEVENT BEGIN:VEVENT SUMMARY:Study of the Spin/CP properties of the Higgs coupling to W-bosons with ATLAS at the LHC DTSTART:20221026T093000Z DTEND:20221026T113000Z DTSTAMP:20240329T082742Z UID:197d4da1-f700-4f96-b93c-842c91f68fb0 SEQUENCE:4 CREATED:20220928T083743Z DESCRIPTION:Abstract:Sources of CP violation beyond the Standard Model (SM ) are necessary to account for the observed matter-antimatter asymmetry i n the Universe. Despite the significant progress in the experimental explo ration of the Higgs sector in the last ten years and the overall agreemen t of the current results with the expectations of the SM\, the experimenta l precision is not yet sufficient to constrain anomalous Higgs boson inte ractions. The work presented here focuses on the search for CP violation in the HWW interaction vertex in events where a Higgs boson is produced in association with a W boson\, when the Higgs decays to a pair of b-quark jets and the W boson to a charged lepton and a neutrino. Several groups h ave proposed different observables to search for anomalous couplings in th e HWW vertex. In order to optimise the experimental sensitivity to such c ouplings\, the most promising angular observables proposed in the literatu re were compared to novel machine-learning inference methods that allow b uilding (statistically) optimal observables without approximating the det ector response. The results show that a combination of energy-related and angular observables is competitive with the current version of the tested machine-learning inference techniques.All these methods require the best possible experimental resolution in the measurement of the final state par ticles. The identification of b-jets\, as well as the measurement of thei r energy and momentum\, is very challenging experimentally and requires d edicated calibration samples\, as well as analysis techniques. Collecting large\, unbiased samples of jets for calibration requires an efficient an d optimised jet trigger system. The ATLAS jet trigger was upgraded for Run 3\, introducing full-event scan tracking and calorimeter+track jet recon struction. This presentation will also cover several studies done to stud y and optimise the jet'\;s trigger efficiency and CPU costs. LAST-MODIFIED:20221021T094222Z LOCATION:Online (Meeting ID: 657 2811 7852 Passcode: 716650) URL:http://df.vps.tecnico.ulisboa.pt/eventos/study-of-the-spincp-propertie s-of-the-higgs-coupling-to-w-bosons-with-atlas-at-the-lhc/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
Sources of CP violation beyond the Standard Mod
el (SM) are necessary to account for the observed matter-antimatter asymm
etry in the Universe. Despite the significant progress in the experimental
exploration of the Higgs sector in the last ten years and the overall ag
reement of the current results with the expectations of the SM\, the exper
imental precision is not yet sufficient to constrain anomalous Higgs boso
n interactions. The work presented here focuses on the search for CP viol
ation in the HWW interaction vertex in events where a Higgs boson is produ
ced in association with a W boson\, when the Higgs decays to a pair of b-
quark jets and the W boson to a charged lepton and a neutrino.
Several groups have proposed different observables to search for anom
alous couplings in the HWW vertex. In order to optimise the experimental
sensitivity to such couplings\, the most promising angular observables pro
posed in the literature were compared to novel machine-learning inference
methods that allow building (statistically) optimal observables without
approximating the detector response. The results show that a combination o
f energy-related and angular observables is competitive with the current
version of the tested machine-learning inference techniques.
All these methods require the best possible experimental resolution in th
e measurement of the final state particles. The identification of b-jets\
, as well as the measurement of their energy and momentum\, is very challe
nging experimentally and requires dedicated calibration samples\, as well
as analysis techniques. Collecting large\, unbiased samples of jets for
calibration requires an efficient and optimised jet trigger system. The AT
LAS jet trigger was upgraded for Run 3\, introducing full-event scan trac
king and calorimeter+track jet reconstruction. This presentation will also
cover several studies done to study and optimise the jet'\;s trigger
efficiency and CPU costs.
Experimental High-
Energy Physics\, especially the Large Hadron Collider programme at CERN\,
is one of the most computationally intensive activities in the world. This
demand is set to increase significantly with the upcoming High-Luminosity
LHC\, and even more in future machines\, such as the Future Circular Coll
ider.
As a consequence\, event reconstruction\, and in particula
r jet clustering\, is bound to become an even more daunting problem\, thus
potentially challenging present day computing resources. In this talk\, I
present the two quantum algorithms to tackle this problems and\, in parti
cular\, the first digital quantum algorithm to for jet clustering\, openin
g the way for digital quantum processors to address this challenging probl
em. Furthermore\, we show that\, at present and future collider energies\,
our algorithms have at least comparable complexity relative to the classi
cal state-of-the-art $k_t$ clustering algorithm
Resumo
A fusão nuclear controlada é umas das soluçõ
es mais promissoras para o aumento da procura por formas mais sustentávei
s de produção de energia eléctrica à escala global. No caminho a perco
rrer até à comercialização de energia eléctrica produzida através da
fusão\, o reactor DEMO\, desenvolvido pelo consórcio EUROFusion\, é um
passo intermédio entre o ITER (em construção) e os reactores comerciai
s do futuro. Tokamaks de grandes dimensões como o ITER e o DEMO requerem
redes complexas de sistemas de diagnóstico\, que permitam controlar o pla
sma de forma fiável por longos períodos de operação.
Entre e
stes\, a reflectrometria de microondas já demonstrou ser uma forma altern
ativa de controlo\, capaz de monitorizar a densidade\, a posição e a for
ma do plasma com elevada resolução espacial e temporal. Esta tese aprese
nta estudos de design e engenharia para dois sistemas de diagnóstico dese
nvolvidos pelo IPFN/IST: o sistema de reflectometria de posição de plasm
a (PPR) do ITER e um sistema com múltiplos reflectómetros proposto para
o DEMO. Devido à natureza das medições\, alguns dos componentes destes
sistemas estarão expostos directamente ao plasma\, sujeitos a elevados fl
uxos de neutrões de alta energia (14 MeV) que contribuirão para as carga
s térmicas nos componentes e poderão ter como efeito alterar as propried
ades dos materiais\, pondo em risco a sua integridade mecânica durante os
períodos de funcionamento dos reactores.
Por esta razão\, est
udos complexos de design (envolvendo neutrónica\, análises termo-mecâni
cas e simulações electromagnéticas) são cruciais para garantir que os
diagnósticos sobrevivem aos ambientes de radiação do ITER e do DEMO sem
comprometer o seu desempenho. Para o sistema PPR do ITER\, o software ANS
YS Mechanical foi usado para estimar as temperaturas de operação dos com
ponentes mais expostos\, em duas posições distintas\, conhecidas como ga
ps 4 e 6. Nas configurações estudadas\, os resultados mostram que as ant
enas do sistema PPR estariam sujeitas a temperaturas superiores ao limite
estabelecido pelo ITER para o aço inoxidável sob 1 irradiação\, mesmo
após várias tentativas de optimização.
Tendo em conta estes
resultados\, diferentes materiais foram propostos para as antenas. Apesar
de a Organização ITER ter descontinuado o desenvolvimento do sistema PPR
\, o conhecimento adquirido durante os estudos de integração e desenvolv
imento continua a ser válido para o desenho do sistema de reflectometria
proposto para o DEMO. Para este sistema\, um conceito de integração prop
osto previamente – Diagnostics Slim Cassette (DSC) – foi desenhado e a
valiado. Os códigos CATIA V5\, MCNP e ANSYS foram usados para desenhar o
sistema e estimar fluxos de neutrões e radiação gama\, cargas térmicas
e temperaturas de operação\, assim como o impacto que essas condições
de operação terão nas medições de reflectometria.
As anál
ises nucleares e termo-mecânicas apresentadas neste trabalho demonstram a
viabilidade do conceito e a capacidade do sistema para operar no ambiente
de radiação do reactor DEMO\, de acordo com os padrões estabelecidos p
elo código RCC-MR. Este resultado é obrido com uma configuração simpli
ficada do sistema de arrefecimento\, possível de fabricar com técnicas c
onvencionais. Os resultados e as metodologias implementadas nesta tese pod
em servir como directizes para outros sistemas de diagnostico\, nomeadamen
te aqueles em que a DSC possa servir como possível solução de integraç
ão.
Os veículos elétricos são considerados uma opção mais vi
ável no combate da emissão dos gases de efeito de estufa no sector de tr
ansporte. No entanto\, um dos problemas que impedem a adoção global dos
veículos elétricos é a autonomia limitada\, o que leva ao fenómeno de
“ansiedade de alcance”. A produção fotovoltaica integrada em veícul
os elétricos é uma possível alternativa para este problema.
A
o incorporar a tecnologia fotovoltaica no teto do veículo\, o sistema de
baterias do mesmo pode ser carregado durante a condução ou mesmo quando
o veículo está em estacionamento. Por outro lado\, o emprego desta tecno
logia permite subdimensionar as baterias\, originando uma poupança direct
a no investimento capital do veículo e nos custos de operação.
O foco principal desta tese é\, pois\, oti
mizar a gestão de energia das baterias dum Riquexó elétrico com base nu
m histórico diário de percursos\, quantificando a viabilidade tecno-econ
ómica quanto à existência de mercado para estes veículos. Com o sistem
a proposto\, implementado e estudado nesta tese foi possível observar\, n
um dia típico ensolarado em meia estação\, um aporte em média dum supl
emento de 35% da energia elétrica consumida pelo veículo. A análise eco
nómica do sistema proposto previu um Retorno de Investimento (ROI) de 185
% ao longo da vida útil do veículo de 6 anos.
Note-se que\, devido ao cariz sazonal do veículo em que é e sperado um maior consumo em dias de sol devido às suas características t urísticas\, estas poupanças podem ser levadas praticamente ao limite dum a redução similar à capacidade energética das baterias.
END:VEVENT BEGIN:VEVENT SUMMARY:Data acquisition system for the magnetics diagnostics in COMPASS-U DTSTART:20221027T113000Z DTEND:20221027T133000Z DTSTAMP:20240329T082742Z UID:ec8ca321-0290-48dd-b37d-3a23551daca0 SEQUENCE:5 CREATED:20221025T151914Z DESCRIPTION:COMPASS-U will be a new magnetic fusion experiment\, designed to support the operation of ITER and to serve as a stepping stone on the r oad to DEMO\, addressing key challenges in its construction and design. As such it will be a high magnetic field device (5T)\, supporting high densi ties and power fluxes relevant to ITER and DEMO. As with any magnetic fusi on device magnetic diagnostics are fundamental for both plasma control and scientific studies. The requirements placed on the acquisition system for these diagnostics are not readily found in the market and a custom design has the potential to fulfil them at a lower cost. The design of a data ac quisition system satisfying the requirements of the magnetic diagnostics i n COMPASS-U is presented. The carrier board under design is based on a FPG A SoM and is compatible with existing isolated 2MSPS ADC modules. This mod ule confers flexibility to the design and allows the functionality of the board to be extended to suit other data acquisition applications requiring a high number of channels and a high volume of data at a low cost per cha nnel.(Password: 1911\, Meeting ID: 932 4201 1237) LAST-MODIFIED:20221103T160921Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/data-acquisition-system-for-t he-magnetics-diagnostics-in-compass-u/ X-ALT-DESC;FMTTYPE=text/html:COMPASS-U will be a
new magnetic fusion experiment\, designed to support the operation of ITE
R and to serve as a stepping stone on the road to DEMO\, addressing key ch
allenges in its construction and design. As such it will be a high magneti
c field device (5T)\, supporting high densities and power fluxes relevant
to ITER and DEMO. As with any magnetic fusion device magnetic diagnostics
are fundamental for both plasma control and scientific studies. The requir
ements placed on the acquisition system for these diagnostics are not read
ily found in the market and a custom design has the potential to fulfil th
em at a lower cost.
The design of a data acquisition system sati
sfying the requirements of the magnetic diagnostics in COMPASS-U is presen
ted. The carrier board under design is based on a FPGA SoM and is compatib
le with existing isolated 2MSPS ADC modules. This module confers flexibili
ty to the design and allows the functionality of the board to be extended
to suit other data acquisition applications requiring a high number of cha
nnels and a high volume of data at a low cost per channel.
(
Password: 1911\, Meeting ID: 932 4201 1237)
Abstract:The Weiss variation formalism in mechanics and classical field theory c
oncerns action variations that include explicit endpoint/boundary displace
ments. The Weiss variation is useful in field theory because it can be use
d to obtain expressions for the conjugate momenta and Hamiltonian without
performing an explicit 3+1 decomposition beforehand. In this talk\, I revi
ew the Weiss variation in mechanics\, classical field theory\, and in grav
itation.
In general relativity\, one can recover (by way of an a
uxiliary connection formalism) a tensorial generalization of the Einstein
canonical energy-momentum pseudotensor\, as well as a reference-dependent
Hamiltonian. In addition to discussing the Weiss variation in general rela
tivity\, I comment on some applications of the Weiss variation formalism f
or modified gravity theories.
We review all the d
ifferent direct and indirect approaches that lattice QCD has beenemploying
to study multiquarks\, focusing in the tetraquarks with heavy quarks. Wea
lso briefly review the experimental progress in observing tetraquarks\, an
d the mostrepresentative models of tetraquarks\, comparing them with the r
esults of lattice QCD.
Since the discovery of quarks and the deve
lopment of the QCD theory\, there has beena large interest in exotic hadro
ns\, initiated by the tetraquark models developed byJaffe in 1974. In the
new millennium\, this interest exploded with several experimentaldiscoveri
es of tetraquark resonances with heavy quarks\, starting with the $Z_c$ an
d$Z_b$.
Moreover there is a second class of tetraquarks such as
the $T_{bb}$\,boundstates in the sense of having no strong decays. Very re
cently\, the narrow$T_{cc}$ tetraquark first predicted with quark models i
n 1982 Richard et al\, wasobserved experimentally. Lattice QCD\, being a f
irst principle approach to solve nonperturbative QCD\, has been crucial no
t only to compute precise results\, but also tomotivate and inspire resear
ch in hadronic physics\, with particular interest in exotichadrons.
So far\, lattice QCD has not yet been able to comprehend the $Z$ class
oftetraquarks\, while it predicted the $T$ class of tetraquarks. New meth
ods are beingdeveloped to determine the masses\, decay widths and decay pr
ocesses of tetraquarks.
ABSTRACT:
With the advent of Gravitational Wave (GW) astr
onomy a new door into learning about properties of matter has been opened.
In particular\, gravitational waves coming from a first order phase trans
itions are expected to be detectable by next generation experiments.
<
br/> These are assumed to proceed via the nucleation\, expansion and colli
sion of bubbles. An accurate prediction of the spectrum implies computing
out-of-equilibrium properties of quantum field theories\, which are challe
nging even at weak coupling.
This offers a golden opportunity fo
r holography to make an impact on astrophysics and cosmology. In this talk
I will review recent progress in the context of cosmological phase transi
tions\, including a possible alternative mechanism of GW emission\, and ne
utron star mergers.
The ability to cont
rol and manipulate the strength of correlations in
quantum matter is o
ne of the central questions in condensed matter
physics today. While p
ressure\, chemical doping\, or magnetic field have
served as conventio
nal tuning knobs for a wide class of correlated
systems\, the ability
to twist van der Waals materials has recently
emerged as a novel schem
e to engineer strong correlations and tune
electronic properties.
For example\, when two sheets of graphene are
twisted to a "
\;magic angle\,"\; the kinetic energy of the electronic degrees
of
freedom vanishes and\, as a result\, interaction effects dominate. Thishas now been demonstrated experimentally following the discovery of
superconductivity in close proximity to correlated insulating phases inmagic-angle graphene.
In this talk\,
I will first discuss our theory that describes the
magic-angle phenome
na as a universal property of Dirac points in an
incommensurate potent
ial.
This allows us to generalize the magic-angle
effect to
a wide class of models and distinct physical settings\, such as
ultra-
cold atomic gases\, trapped ions\, and metamaterials. This general
per
spective will then be used to demonstrate how unconventional
supercond
uctors can be manipulated via a twist. These results will then
be appl
ied to describe recent experiments on twisted slabs of the
high-temper
ature superconductor
In the first part
of this talk\, I will describe what has kept me and my collaborators busyo
ver the past year. My goal here is to keep you - the local community - up
to date onwhat we have been doing and foster discussions and collaboration
s. In the secondpart of the talk\, I will focus on one of the ongoing scie
ntific projects that is part ofMiguel Oliveira’s Ph.D. thesis.
In this work\, we ask what is the fate of a Mott insulatorwhen a bias vol
tage\, \\delta\\mu\, is applied across the system. Our goal is to understa
ndwhat kinds of non-equilibrium phases are realized as the voltage increas
es and what isthe nature of the non-equilibrium quantum phase transitions
between them.
Weconsider a model system consisting of a half-fil
led t-V chain coupled to leads\, thatfeatures spineless fermions with near
est neighbor interactions and where both theequilibrium (\\delta\\mu=0) an
d the Markovian (\\delta\\mu\\to\\infty) limits are known. Iwill describe
our progress and the challenges we have been facing.
Nesta tese consideramos uma das mais simples extensões do se
tor escalar do Modelo Standard: Modelos de N dubletos de Higgs (NHDM). Pri
meiro estudamos o potencial escalar mais geral com uma simetria exata. Pro
vamos que tal modelo exibirá um limite de desacoplamento se e só se o v
ácuo também satisfizer a mesma simetria. Esta propriedade geral também
é mostrada independente e explicitamente para modelos com três dubletos
de Higgs\, considerando em detalhe todos os modelos com uma simetria e os
seus possíveis vácuos.
Depois\, estudamos dois 2HDM invariante
s sob as simetrias Z2xPi2 e U(1)xPi2. Para o primeiro\, provamos que não
é possível estender a simetria para os fermiões de forma compatível co
m as observações experimentais (massas de quarks\, ângulos de mistura\,
e Jcp não nulos)\, enquanto que para o segundo mostramos que é possíve
l\, existindo apenas uma extensão.
Seguidamente\, consideramos
um 3HDM com uma simetria A4 exata. Fornecemos as condições analíticas c
ompletas\, necessárias e suficientes para um ponto ser mínimo global nas
direções neutras\, discutindo também algumas subtilezas subjacentes qu
e salientamos através de exemplos numéricos.
Após isto\, estu
damos as direções que quebram a carga elétrica e apresentamos condiçõ
es analíticas suficientes que garantem Boundedness from below (BFB
). Para estas direções\, baseados num conjunto extenso de simulações n
uméricas\, discutimos também uma conjetura sobre BFB.
Finalmen
te\, consideramos a adição de termos\, ao potencial escalar\, que quebra
m suavemente a simetria A4 num modelo com três dubletos. Nesse\, estudamo
s numericamente as extensões de A4 ao setor fermiónico\, concluindo acer
ca da sua compatibilidade com as observações experimentais.
Resumo:
Neste trabalho estudamos u
ma extensão do Modelo Padrão ao comparar dois modelos que explicam a ori
gem de indícios de violação de universalidade de sabor dos leptões par
a o decaimento b sl+l-\, o momento anómalo do muão e o problema da maté
ria escura (ME).
O decaimento do quark e a anomalía do muão s
ão explicados através de diagramas com loops onde participam os c
andidatos a ME. Para além dos campos do Modelo Padrão\, os modelos têm
um campo fermiónico sem cor\, um campo escalar sem cor e um com cor. Num
dos modelos\, o fermião é um dubleto de e os escalares são singletos de
enquanto no outro modelo o fermião é um singleto de e os escalares são
dubletos de .
Após estudarmos a fenomenologia de sabor e maté
ria escura dos modelos\, fizemos um scan de forma a encontrar o esp
aço de parâmetros dos modelos que explica os três fenómenos de nova f
ísica simultaneamente. Concluímos que ambos os modelos conseguem explica
r não só todos os problemas mencionados anteriormente mas também outros
problemas de sabor e ME.
Contudo\, existem diferenças cruciais
na forma como as restrições na ME afetam os dois modelos\, resultando n
uma diferença considerável nos valores permitidos para a massa de ME.
Quantificar as escalas da transição entre os regimes pertur
bativo (pQCD) e não-perturbativo (npQCD) da Cromodinâmica Quântica é u
m problema de raiz da Física de Partículas. Enquanto que pQCD aplica-se
aos partões (quarks e gluões)\, partículas finais (detetáveis) enquadr
am-se no regime npQCD. Estas designam-se por hadrões\, partículas compos
tas produzidas via hadronização.
Para adquirir conhecimento re
lativo ao processo de hadronização\, esta tese propõe o uso de jets com
o ferramenta de análise\, que são estruturas de partículas finais às q
uais sequências de clusterings são atribuídas como proxies da história
evolutiva das partículas.
Usando jets
de diferentes regiões cinemáticas e colisões de diferentes energias de
centro de massa como instrumentos de seleção da espécie partónica pre
dominante na iniciação dos jets\, são realizados estudos de subestrutur
a que revelam que gluões produzidos em colisões energéticas tendem a in
iciar jets mais largos\, simétricos e céleres que os quarks.
E
ste documento contém estudos adicionais focados na fração de momento gr
oomed\, que mede a simetria de uma emissão em termos de momento transvers
al\, e no tempo de formação\, um proxy para as escalas temporais das emi
ssões. Estes mostram que a seleção de jets baseada em tempos de formaç
ão permite a identificação da etapa de declustering na qual as duas par
tículas carregas mais energéticas se desacoplam. Também revelam que est
e processo marca claramente na sequência de clusterings a transição de
propriedades típicas de pQCD para propriedades atípicas deste regime.
Abstract:
Cons
equence system. Consequence system induced by a calculus and by a
se
mantics. Soundness and completeness. Classical and intuitionistic logics.<
br/>Metatheorems.
Password Acesso
Zoom: 464728
Estudamos sistemas dissipativos Markovianos descritos por
Liouvilianos fermiónicos e quadráticos. Apresentamos um novo esquema de
vetorização que nos permite obter os resultados principais presentes em
[1] para o espectro e estado estacionário de um Liouviliano quadrático.
Inicialmente consideramos o caso de Liouvilianos genéricos construídos
a partir de um Hamiltoniano quadrático aleatório e canais de dissipaçã
o lineares e também aleatórios.
Variando a intensidade da diss
ipação e o número destes canais por fermião\, m=M/(2NF)\, encontramos
duas fases distintas onde o suporte do espectro single-body tem uma ou dua
s regiões conexas. No regime fortemente dissipativo\, esta transição oc
orre a m=1/2 e é concomitante com uma mudança qualitativa tanto no estad
o estacionário como no hiato espectral.
Além disso\, estudamos sistemas de transporte\, descritos por Liouvilian
os quadráticos\, sob medições contínuas ou ruído. Primeiro\, foi estu
dado uma cadeia acoplada a reservatórios Markovianos com dephasing induzi
do por ruído estocástico ou medições contínuas locais. Foi fornecida
uma abordagem alternativa aos resultados obtidos em [2].
Para um
a análise mais profunda foi estudado o formalismo Large Deviations e dese
nvolveu-se um método capaz de eliminar instabilidades numéricas na imple
mentação de evoluções de matrizes densidade geradas por superoperadore
s gerais\, quadráticos e que não conservam o traço. Este método é out
ro resultado original desta tese e acaba por ter aplicações consideravel
mente mais amplas\, pois determina como proceder de forma geral para obter
a evolução temporal de qualquer sistema quadrático\, aberto ou fechado
sob ruído ou medições. Por fim\, aplicamos este método a uma cadeia f
ermiónica com medições continuas.
Abstract:
Becau
se of their common origin\, it is expected (or assumed) that the compositi
on of planet building blocks should (to a first order) correlate with stel
lar atmospheric composition\, especially for refractory elements.
In fact\, information on the relative abundance of refractory and major
rock-forming elements such as Fe\, Mg\, Si are commonly used to improve in
terior estimates for terrestrial planets and has even been used to estimat
e planet composition in different galactic populations.
However\
, there is no direct observational evidence for the aforementioned expecta
tion/assumption and was even recently questioned. In this talk I'\;ll
present our latest results where showed that the composition of the planet
building blocks indeed correlates with the properties of the rocky planet
s.
Resumo:
AMBER é uma experiência f utura de alvo fixo no CERN. Foi aprovada recentemente e um dos objetivos d e física da primeira fase é o estudo do processo Drell-Yan induzido por um pião.
Drell-Yan consiste na aniquilação
de um quark e um antiquark originando um fotão virtual que decai no esta
do final para um par de muões com cargas opostas. Este processo garante u
m acesso privilegiado à estrutura do pião. Desta forma\, a contribuiçã
o da valência\, do mar e dos gluões no pião serão caracterizadas com p
recisão sem precedente. AMBER usará feixes de piões de alta intensidade
e energia\, de ambas as cargas\, a interagir com diferentes alvos nuclear
es.
A configuração experimental de
AMBER é baseada na da experiência COMPASS\, introduzindo upgrades signi
ficativos ao espectrómetro já existente. Assim\, a otimização da regi
ão do alvo de AMBER para as medidas de Drell-Yan está a ser estudada e
é o objetivo deste trabalho.
Neste
trabalho\, introduzimos uma cadeia de simulação de Monte Carlo que perm
ite a simulação do processo físico e do espectrómetro\, a resposta dos
detetores e a reconstrução dos dados obtidos. Assim\, vamos estudar o i
mpacto da introdução de detetores de vértice e como diferentes posiçõ
es\, geometrias e segmentações afetam os resultados.
Neste estudo\, o detector de microstrips de silício F
VTX parece a opção mais sólida para o detetor de vértice. A escolha ba
seia-se nos valores obtidos para a resolução em massa e na posição Z d
o vértice\, assim como na aceitância global de dimuões.
(Contactar Ana Bela
Cardoso para password) ana.bela.cardoso@tecnico.ulisboa.pt
Um dos
passos mais importantes na indústria de dispositivos magnetoresistivos
é a caracterização do comportamento magnético de multi-camadas de film
es através de curvas de histerese. É necessário quantificar várias pro
priedades magnéticas para a fabricação bem controlada de novas aplicaç
ões\, como anisotropia magnética\, acoplamento de troca\, etc\, que são
críticos para a operação de dispositivos.
Estas são determi
nadas por técnicas sensíveis de magnetometria\, uma das quais sendo o ef
eito magneto-óptico de Kerr que faz uso de luz polarizada. Tal montagem p
ossui a vantagem\, por exemplo\, de ser capaz de realizar medidas locais c
om boa resolução espacial\, em contraste com o magnetómetro de amostra
vibrante ou o dispositivo de interferência quântica supercondutora\, com
tempos de aquisição rápidos e requerendo nada mais que uma montagem si
mples de bancada. Desta forma\, este é o magnetómetro ideal para complem
entar as capacidades e objetivos de investigação do INESC MN.
<
br/>De modo a conceber a montagem\, uma análise teórica juntamente com s
imulações numéricas foram realizadas para provar que a medida de uma cu
rva de histerese era possível e como esta se relacionava com a intensidad
e do sinal\, a rotação de Kerr e a elipticidade de Kerr. Para além diss
o\, estas também cobriram os requisitos necessários à montagem em termo
s de ruído\, estrutura de amostras e eletroíman. Concluiu-se que a medid
a ideal deverá ser realizada através de uma medida diferencial com ampli
ficador lock-in\, usando usando uma camada até 30 nm no topo da hetero-es
trutura. Para além disso\, verificou-se que\, por forma a obter campos ma
gnéticos fortes\, da mesma ordem que os campos de inversão em junções
de efeito de túnel\, a solução de eletroíman a implementar deverá inc
luir um núcleo ferromagnético.
Depois\, o m
agnetómetro foi construído nas geometrias transversal e longitudinal de
acordo com a análise anterior. A presença de obstáculos relacionados co
m o ruído nos circuitos de aquisição DC e AC propostos\, levaram uma ve
z mais à aplicação de um amplificador lock-in na montagem.
Para validar as montagens construídas\, amostras de
NiFe foram depositadas e medidas nas mesmas\, demonstrando a sua sensibil
idade a variações da magnetização das amostras. No entanto\, a rotaç
ão de Kerr não foi possível medir na geometria longitudinal\, muito pro
vavelmente devido a ruído proveniente do divisor de feixe polarizado. Adi
cionalmente\, observou-se que a deposição de CoFe/Ta e CoFe/Ru para espe
ssura variável da camada de topo e a sua subsequente medida na montagem l
ongitudinal\, coincidiam muito bem com os resultados das simulações.
Apesar de ainda apresentar espaço par a melhorias\, a montagem tem vindo a mostrar continuamente a sua precisão e utilidade na caracterização de estruturas magnéticas. Ademais\, tem o potencial para a implementação de mais funções como o acréscimo de uma nova geometria\, a inclusão de um ambiente controlado ou a observaç ão de domínios magnéticos através de um dispositivo de carga acoplada.
END:VEVENT BEGIN:VEVENT SUMMARY:Building up DNA (and other molecules)\, bit by bit DTSTART:20221123T153000Z DTEND:20221123T173000Z DTSTAMP:20240329T082742Z UID:ab4e83e0-684f-479d-835d-1dd3bf865f87 SEQUENCE:1 CREATED:20221117T143826Z DESCRIPTION: The properties of large aggregates of particles\, be they col loidal clusters ormacromolecules\, often depend crucially on the precise a rrangement of their buildingblocks. Examples are the nature of the de-mixi ng in reacting polymer blends\; theability of some elastomers to exhibit s train-induced periodic textures\; or the selfhealing nature of some copoly mers over a narrow range of compositions. However\, theactual sequence of building blocks is not usually experimentally accessible: knowing itwould allow\, e.g.\, the reverse engineering of structures with desirable behavi ours. Wedevelop a simple theory that treats self-assembly as reversible ch emical reactions. Wethen apply this to the assembly of DNA copolymers from two types of duplexes\, asdescribed by the oxDNA model. We find that the theory reproduces well the statisticsof chain lengths from simulations. Ou r results suggest that theories incorporating verylimited molecular detail may be useful for predicting the broad equilibrium features\,and even som e kinetic aspects\, of copolymerisation. LAST-MODIFIED:20221117T143826Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/building-up-dna-and-other-mol ecules-bit-by-bit/ X-ALT-DESC;FMTTYPE=text/html: The properties of
large aggregates of particles\, be they colloidal clusters ormacromolecule
s\, often depend crucially on the precise arrangement of their buildingblo
cks. Examples are the nature of the de-mixing in reacting polymer blends\;
theability of some elastomers to exhibit strain-induced periodic textures
\; or the selfhealing nature of some copolymers over a narrow range of com
positions.
However\, theactual sequence of building blocks is no
t usually experimentally accessible: knowing itwould allow\, e.g.\, the re
verse engineering of structures with desirable behaviours.
Wedev
elop a simple theory that treats self-assembly as reversible chemical reac
tions. Wethen apply this to the assembly of DNA copolymers from two types
of duplexes\, asdescribed by the oxDNA model. We find that the theory repr
oduces well the statisticsof chain lengths from simulations.
Our
results suggest that theories incorporating verylimited molecular detail
may be useful for predicting the broad equilibrium features\,and even some
kinetic aspects\, of copolymerisation.
O tratamento do infinito nulo futuro na Relatividade Numéric
a é ainda um problema em aberto. A sua relevância deve-se ao facto de se
r o único “local” no espaço-tempo onde a radiação gravitacional po
de ser medida de forma inequívoca\, e de corresponder também à idealiza
ção adequada de observadores de eventos astrofísicos. A precisão das f
ormas de onda extraídas das simulações numéricas é crucial para estim
ar a correta propriedades das fontes de radiação gravitacional observada
s pelos interferómetros.
Atualmente\, essas formas de onda são
calculadas por extrapolação ou por extração/evolução Cauchy-caracte
rística. No entanto\, esses métodos são insatisfatórios do ponto de vi
sta de primeiros princípios. Neste trabalho\, adotamos uma abordagem alte
rnativa – o método hiperboloidal –\, em que o espaço-tempo é foliad
o em hipersuperfícies espaciais que se estendem até ao infinito nulo fut
uro. Para isso\, introduzimos novas coordenadas que compactificam o espaç
o-tempo. Nestas coordenadas\, as equações de onda têm termos formalment
e singulares\, o que podemos superar considerando a taxa de decaimento dos
campos e redimensionando-os tal que as equações se tornem regulares no
infinito nulo futuro.
Para entender melhor a taxa de decaimento
dos campos\, apresentamos o modelo good-ugly e mostramos que reprod
uz o comportamento das equações linearizadas de Einstein. Implementamos
a abordagem hiperboloidal para as equações do modelo e mostramos que ela
s são regulares no infinito nulo futuro.
Para a implementação
numérica\, usamos o código NRPy+\, e resolvemos as equações em primei
ra ordem no tempo e no espaço com dados iniciais axialmente simétricos n
uma grelha que não inclui os extremos. Verifica-se convergência\, indica
ndo um resultado bem-sucedido. Uma abordagem semelhante pode ser feita par
a a Relatividade Geral completa\, embora com complicações adicionais.
Através das colisões de iões pesados\, tal como PbPb\, é
possível produzir o plasma de Quarks e Gluões (QGP) em aceleradores de p
artículas\, como é o caso do Large Hadron Colider (LHC). A partir do fen
ómeno de jet quenching\, em que partões muito energéticos formados em s
imultâneo com o plasma interagem com este\, dando origem a jets de hadrõ
es que são modificados relativamente às colisões em que tal meio não
é criado (i.e colisões pp)\, é possível estudar as propriedades do QGP
.
Como tal\, é crucial a existên
cia de simuladores de Monte Carlo\, como o JEWEL\, que permitam explorar a
fenomenologia de jet quenching. Contudo\, o JEWEL não está idealizado p
ara lidar com colisões não centrais e/ou entre núcleos mais leves. Esta
s últimas\, embora estejam associadas com a produção de menos QGP\, abr
em portas para o estudo de processos mais raros e permitem mais precisão
na medição de certos observáveis de jets. Inclusivamente\, colisões OO
vão ser realizadas no LHC durante a run 3.
Este trabalho tentou otimizar o funcionamento do JEWEL para o li
mite da colisão de núcleos leves e/ou periféricas\, substituindo o mode
lo de inicialização do meio\, baseado na aproximação ótica\, por um m
ais realista e adequado a este limite\, baseado no modelo de Glauber Monte
Carlo.
Posteriormente\, foi realizado um estudo intensivo de co
mparação entre estes dois modelos\, onde se pode concluir que o tratamen
to mais realista conduz a diferenças substanciais no evento médio e nos
valores obtidos para observáveis. Finalmente\, utilizou-se o modelo const
ruído para estudar variáveis de sub-estrutura de jets\, em colisões de
núcleos leves.
Resumo
O início da nova
fase de operação do LHC (Run 3)\, e consequente anúncio da futura reali
zação das primeiras colisões de núcleos leves\, marca o princípio de
uma nova era na história da Física de Partículas\, a qual exige aprofun
dar os estudos sobre colisões de sistemas pequenos. Contudo\, esta tarefa
não é fácil\, pois atualmente os geradores de eventos Monte Carlo usad
os para explorar a fenomenologia do jet quenching falham no tratamento dos
aspetos geométricos de jet quenching em sistemas pequenos.
Daqui surge o primeiro objetivo desta tese: mod
ificar o código do gerador de eventos Monte Carlo\, JEWEL\, de forma a me
lhorar a sua performance no tratamento de sistemas pequenos. Tal foi conse
guido\, essencialmente\, através da alteração do modelo implementado em
JEWEL para descrever a geometria da colisão inicial\, o modelo Ótico de
Glauber (MOG)\, substituindo-o pelo modelo Monte Carlo de Glauber (MMCG).
Verificou-se que as principais diferenças entre os dois códig
os ocorrem em colisões de núcleos leves e/ou em colisões periféricas\,
dado que o MOG\, para além de não ser válido para núcleos leves\, ign
ora a existência de flutuações na geometria da colisão inicial.
Por fim\, usando este novo gerador de eve ntos\, realizou-se uma análise comparativa do jet quenching em sistemas d e geometria diferente\, mas tamanho igual\, concluindo-se que\, no que diz respeito à perda de energia por jet quenching\, o Fator de Modificação Nuclear\, \, é sensível à geometria do meio.
END:VEVENT BEGIN:VEVENT SUMMARY:Towards low noise\, biaxial magnetic field imaging of electrical c urrents with magnetic tunnel junctions DTSTART:20221124T103000Z DTEND:20221124T123000Z DTSTAMP:20240329T082742Z UID:192cf7db-89a0-472a-8761-37a258c4bae1 SEQUENCE:3 CREATED:20221122T095823Z DESCRIPTION:ResumoNesta dissertação\, Junções de Efeito de Túnel (JET s) são exploradas no contexto de aplicações de Análise Não-Destrutiva por meio de inspeção do campo magnético produzidos por correntes eléc tricas em dispositivos microeletrónicos. Um novo protótipo de sensores J ET é proposto e testado\, combinando deteção biaxial a baixo ruído do campo magnético. Um solução que combine deteção simultânea de duas c omponentes a baixo ruído do campo magnético é favorecida em detrimento da melhoria da resolução espacial\, o que é sustentado pelos padrões d e integração microelectrónica de estado-da-arte e por simulações das assinaturas magnéticas produzidas por configurações de correntes elétr icas simples encontradas no contexto de falhas em microelectrónica. Os se nsores baseados em JETs incorporam barreiras cristalinas de MgO\, tendo si do depositados por pulverização catódica em magnetrão\, ao que se segu iu a sua padronização em pilares com diferentes fatores de forma de modo a linearizar a sua resposta magnética. Estes pilares foram dispostos em série\, em diferentes geometrias. Seguiu-se um único passo de recoziment o na presença de um campo magnético aplicado a 45º\, de forma a definir uma direção de referência comum entre os sensores. Simetria nas propri edades de magnetotransporte entre sensores de eixos diferentes\, assim com o robustez contra campos cruzados e sensitividades na zona linear osciland o entre 10-20 % / mT foram obtidos após fabricação. Um elevado acoplame nto foi medido ao longo das direções sensíveis\, para o qual diversas h ipóteses de origem são avançadas e confrontadas com um modelo de Stoner -Wohlfahrt para o sistema em questão. Finalmente\, medições de ruído f oram efetuadas na ausência de campo\, a partir das quais os parâmetros d e qualidade foram calculados\, tendo sido inferiores aos necessários na g ama de aplicações a médio e longo alcance. Um reduzido produto resistê ncia-área e anisotropia uniaxial induzida na camada livre das JETs são e lencados como parâmetros fulcrais para uma abordagem bem sucedida ao comp lexo desafio de deteção biaxial a baixo ruído do campo magnético com J ETs\, cujo recozimento é feito num só passo\, de modo a definir as duas direções sensíveis ortogonais. LAST-MODIFIED:20221124T090541Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/towards-low-noise-biaxial-mag netic-field-imaging-of-electrical-currents-with-magnetic-tunnel-junctions/ X-ALT-DESC;FMTTYPE=text/html:Resumo
Nesta dissertação\, Junções de Efeito de Túne
l (JETs) são exploradas no contexto de aplicações de Análise Não-Dest
rutiva por meio de inspeção do campo magnético produzidos por correntes
eléctricas em dispositivos microeletrónicos. Um novo protótipo de sens
ores JET é proposto e testado\, combinando deteção biaxial a baixo ruí
do do campo magnético.
Um solução que combine deteção simul
tânea de duas componentes a baixo ruído do campo magnético é favorecid
a em detrimento da melhoria da resolução espacial\, o que é sustentado
pelos padrões de integração microelectrónica de estado-da-arte e por s
imulações das assinaturas magnéticas produzidas por configurações de
correntes elétricas simples encontradas no contexto de falhas em microele
ctrónica. Os sensores baseados em JETs incorporam barreiras cristalinas d
e MgO\, tendo sido depositados por pulverização catódica em magnetrão\
, ao que se seguiu a sua padronização em pilares com diferentes fatores
de forma de modo a linearizar a sua resposta magnética.
Estes p
ilares foram dispostos em série\, em diferentes geometrias. Seguiu-se um
único passo de recozimento na presença de um campo magnético aplicado a
45º\, de forma a definir uma direção de referência comum entre os sen
sores. Simetria nas propriedades de magnetotransporte entre sensores de ei
xos diferentes\, assim como robustez contra campos cruzados e sensitividad
es na zona linear oscilando entre 10-20 % / mT foram obtidos após fabrica
ção.
Um elevado acoplamento foi medido ao longo das direções
sensíveis\, para o qual diversas hipóteses de origem são avançadas e
confrontadas com um modelo de Stoner-Wohlfahrt para o sistema em questão.
Finalmente\, medições de ruído foram efetuadas na ausência de campo\,
a partir das quais os parâmetros de qualidade foram calculados\, tendo s
ido inferiores aos necessários na gama de aplicações a médio e longo a
lcance.
Um reduzido produto resistência-área e anisotropia uni
axial induzida na camada livre das JETs são elencados como parâmetros fu
lcrais para uma abordagem bem sucedida ao complexo desafio de deteção bi
axial a baixo ruído do campo magnético com JETs\, cujo recozimento é fe
ito num só passo\, de modo a definir as duas direções sensíveis ortogo
nais.
Abstract:
After
the discovery of the gravitational waves\, gravitational wave physics and
astronomy have provided us new information about strong gravitational phe
nomena and new physics. For example\, speed of gravitational waves\, equat
ion of state at very high dense regions\, constraint on gravitational theo
ries\, and so on.
In order to observe gravitational waves\, we ha
ve used the templates of emitted gravitational waves from a binary system.
However\, we may have a more complicated relativistic dynamical system in
nature\, which may not be integrable. We may expect chaotic behavior in s
uch a system\, for which it is very difficult to make appropriate template
s.
In this talk\, we study chaos in a relativistic dynamical syst
em of compact objects and the gravitational waves emitted from such a syst
em. We then look for some characteristic features of the gravitational wav
es\, which could be used in gravitational wave observation.
We al
so discuss a hierarchical triple system with the Kozai-Lidov mechanism\, w
hich shows the oscillation between the eccentricity of inner binary and re
lative inclination. The evolution curve of the cumulative perihelion shift
\, which is indirect evidence of gravitational wave emission\, will be ben
t since the gravitational waves are emitted strongly when the eccentricity
becomes large. We then show the observability of gravitational waves from
such a triple system. We also consider relativistic effects such as Lense
-Thirring precession.
RESUMO
O trabalho desenvo
lvido nesta tese baseia-se no desenvolvimento de um sistema de infoentrete
nimento a implementar num veículo solar eléctrico e capaz de fornecer in
formação acerca de detalhes gerais da viagem e uma estimativa do seu imp
acto ambiental.
Para isso\, o prime iro passo consistiu em instalar um sistema de paineis solares no veículo eléctrico para aumentar a autonomia do veículo e reduzir a sua dependên cia da rede elétrica. Com isto\, a melhoria da vertente ambiental associa da à utilização do veículo é incentivada.
De seguida\, um sistema de aquisição de dados foi configurado para tra
nsmitir dados adquiridos pelos sensores e relativos aos fenómenos mecâni
cos e elétricos relevantes. O Raspberry Pi foi então configurado
para processar e armanezar os dados que sustentam o sistema de infoentrete
nimento e são analisados para extração de informação.
Por fim\, os sensores e a data adquirida foram uti
lizados para desenvolver o sistema de infoentretenimento. Para obter uma e
scolha mais ponderada de métricas a exibir no sistema de infoentretenimen
to\, realizou-se um estudo de mercado. Com isso\, o sistema de infoentrete
nimento foi desenvolvido e adaptado às necessidades e expetativas dos cli
entes e da empresa\, transmitindo informação acerca dos detalhes gerais
da viagem\, a localização do veículo e o impacto da utilização do mes
mo em termos ambientais e económicos.
Com base nos dados recolhidos durante várias viagens\, a simulação do sistema de infoentretenimento foi desenvolvida com sucesso. Recriando o funcionamento dos sensores\, a plataforma é capaz de processar os dados e produzir as métricas para exibir no sistema de infoentretenimento.
END:VEVENT BEGIN:VEVENT SUMMARY:Time-resolved studies of Warm Dense Titanium: A Bayesian search of coupling parameters DTSTART:20221128T140000Z DTEND:20221128T160000Z DTSTAMP:20240329T082742Z UID:547e7c29-796a-43ba-b929-cc1bfc0ab0d2 SEQUENCE:3 CREATED:20221125T161218Z DESCRIPTION:Plasmas densos e fortemente acoplados são difíceis de modela r graças à dificuldade de tratar as interações quânticas entre muitos corpos a temperaturas elevadas. As colisões electrão-electrão (e-e) e eletrão-ião (e-i) que determinam as propriedades básicas do plasma são difíceis de calcular. Além disso\, isolar e medir as diferentes taxas d e espalhamento em equilíbrio térmico é impossível. Aqui descrevemos um a experiência de "\;pump-probe"\; de femtossegundos em que se tra nsforma uma amostra sólida num plasma para medir os acoplamentos e-e e e- i.Uma configuração experimental\, que consiste num impulso de laser infr avermelho ultracurto (〖10〗^14 W/〖cm〗^2\, 50 fs\, 800 nm)\, foi usa da para criar plasmas de densidade sólida\, com dezenas de eV de temperat ura\, na profundidade de penetração do Titânio. A estrutura eletrónica da amostra aquecida foi sondada com um impulso XUV de energia próxima da borda de absorção M_2\,3. O perfil espacial dos impulsos XUV transmitid os foi gravado numa única medição com uma resolução de 10 μm\, e foi resolvido espacialmente em intervalos de 50 fs\, para um total de dezenas de picossegundos. Um mapa da transmissão XUV para fluências variáveis do laser foi então registado em cada aquisição. Os resultados mostram u ma primeira excitação eletrónica do laser que dá lugar (no regime dos picossegundos) ao processo de equilibração e-i\, com arrefecimento dos e letrões e recuperação da transmissão.Para interpretar os dados experim entais referentes ao primeiro picossegundo\, um modelo foi construído usa ndo teoria cinética de quântica. Assumiu-se um potencial de Coulomb blin dado\, aquecimento uniforme durante a profundidade de penetração\, e um gás de eletrões quase livre a interagir com centros fixos de colisão e outras partículas de gás. Para a resposta temporal mais longa foi utiliz ado um modelo de duas temperaturas.Por fim\, foi realizada uma busca usand o um algoritmo de Monte Carlo para estimar a distribuição posterior dos parâmetros livres. Esta abordagem permite contabilizar adequadamente as m últiplas contribuições de primeira ordem\, as suas correlações e uma melhor compreensão do espaço paramétrico.A partir do modelo de Boltzman n\, pudemos concluir que a termalização e-e é rápida\, o que valida a hipótese usada no modelo de duas temperaturas de que o equilibrio e-e é estabelecido instantaneamente. Encontraram-se correlações entre os parâ metros do modelo de duas temperaturas\, que mostram que um parâmetro de a coplamento e-i constante pode ser uma suposição eficaz numa gama de par âmetros ampla\, se tal constante for ajustada para a intensidade do " \;pumping"\;. Uma correlação positiva foi encontrada entre ε_t e δ _s/δ_0 e correlações negativas prevalecem entre δ_s/δ_0 e G_ei/G_ei^0 e m_eff/m_eff^0. Em geral\, um modelo semelhante a um gás de eletrões l ivre e o modelo de duas temperaturas parecem descrever bem os dados. Os va lores de G_ei aumentam com a temperatura eletrónica\, no domínio que son damos\, mas mantiveram-se na faixa dos valores publicados anteriormente. LAST-MODIFIED:20221125T161319Z LOCATION:Sala P3\, Piso 1- Pavilhão de Matemática URL:http://df.vps.tecnico.ulisboa.pt/eventos/time-resolved-studies-of-warm -dense-titanium-a-bayesian-search-of-coupling-parameters/ X-ALT-DESC;FMTTYPE=text/html:Plasmas densos e fo
rtemente acoplados são difíceis de modelar graças à dificuldade de tra
tar as interações quânticas entre muitos corpos a temperaturas elevadas
. As colisões electrão-electrão (e-e) e eletrão-ião (e-i) que determi
nam as propriedades básicas do plasma são difíceis de calcular. Além d
isso\, isolar e medir as diferentes taxas de espalhamento em equilíbrio t
érmico é impossível. Aqui descrevemos uma experiência de "\;pump-p
robe"\; de femtossegundos em que se transforma uma amostra sólida num
plasma para medir os acoplamentos e-e e e-i.
Uma configuração
experimental\, que consiste num impulso de laser infravermelho ultracurto
(〖10〗^14 W/〖cm〗^2\, 50 fs\, 800 nm)\, foi usada para criar plasmas
de densidade sólida\, com dezenas de eV de temperatura\, na profundidade
de penetração do Titânio. A estrutura eletrónica da amostra aquecida
foi sondada com um impulso XUV de energia próxima da borda de absorção
M_2\,3. O perfil espacial dos impulsos XUV transmitidos foi gravado numa
única medição com uma resolução de 10 μm\, e foi resolvido espacialm
ente em intervalos de 50 fs\, para um total de dezenas de picossegundos. U
m mapa da transmissão XUV para fluências variáveis do laser foi então
registado em cada aquisição. Os resultados mostram uma primeira excitaç
ão eletrónica do laser que dá lugar (no regime dos picossegundos) ao pr
ocesso de equilibração e-i\, com arrefecimento dos eletrões e recupera
ção da transmissão.
Para interpretar os dados experimentais re
ferentes ao primeiro picossegundo\, um modelo foi construído usando teori
a cinética de quântica. Assumiu-se um potencial de Coulomb blindado\, aq
uecimento uniforme durante a profundidade de penetração\, e um gás de e
letrões quase livre a interagir com centros fixos de colisão e outras pa
rtículas de gás. Para a resposta temporal mais longa foi utilizado um mo
delo de duas temperaturas.
Por fim\, foi realizada uma busca usan
do um algoritmo de Monte Carlo para estimar a distribuição posterior dos
parâmetros livres. Esta abordagem permite contabilizar adequadamente as
múltiplas contribuições de primeira ordem\, as suas correlações e uma
melhor compreensão do espaço paramétrico.
A partir do modelo
de Boltzmann\, pudemos concluir que a termalização e-e é rápida\, o qu
e valida a hipótese usada no modelo de duas temperaturas de que o equilib
rio e-e é estabelecido instantaneamente. Encontraram-se correlações ent
re os parâmetros do modelo de duas temperaturas\, que mostram que um par
âmetro de acoplamento e-i constante pode ser uma suposição eficaz numa
gama de parâmetros ampla\, se tal constante for ajustada para a intensida
de do "\;pumping"\;. Uma correlação positiva foi encontrada entr
e ε_t e δ_s/δ_0 e correlações negativas prevalecem entre δ_s/δ_0 e
G_ei/G_ei^0 e m_eff/m_eff^0. Em geral\, um modelo semelhante a um gás de
eletrões livre e o modelo de duas temperaturas parecem descrever bem os d
ados. Os valores de G_ei aumentam com a temperatura eletrónica\, no domí
nio que sondamos\, mas mantiveram-se na faixa dos valores publicados anter
iormente.
Asterosismologia te
m-se revelado\, juntamente com modelização estelar\, uma ferramenta indi
spensável para constringir propriedades de matéria escura. Neste trabalh
o\, estudamos pela primeira vez a influência de produção axiónica na e
volução de uma estrela subgigante -- {KIC} 6933899 -- comparando modelos
computacionais com dados observacionais\, de forma a limitar o acoplament
o $g_{a\\gamma}$. Executamos primeiro uma calibração de alta precisão d
e um modelo estelar\, de modo a obter uma referência para os testes subse
quentes.
Aplicamos seguidamente um diagnóstico de duas fases\,
primeiro utilizando quantidades globais e seguidamente rácios sísmicos d
e alta precisão. Concluímos que a presença de axiões não contraria ob
servações\, pelo contrário melhorando a qualidade dos modelos estelares
para uma certa gama de acoplamentos. Adicionalmente\, concluímos que sis
mologia permite a definição de um limite superior a $g_{a\\gamma} \\leq
6.4\\times 10^{-11} $ GeV$^{-1}$\, compatível com observações a um nív
el de confiança de $68\\%$\, mais estrito que os constrangimentos mais re
centes derivados tanto de observações a aglomerados globulares como de d
etecções diretas.
Sugerimos adicionalmente um limite mais cons
ervador de $g_{a\\gamma} \\leq 1.1\\times 10^{-10} $ GeV$^{-1}$ com um int
ervalo de confiança de $95\\%$. Ademais\, este novo método de diagnósti
co tem a possibilidade de vir a ser aplicado a dados que serão obtidos at
ravés de futuras missões asterosismológicas\, como é o caso da {PLATO}
\, projetada para ser lançada em 2026\, na perspetiva de expandir o nosso
conhecimento sobre axiões.
Resumo
Neste trabalho são estudadas duas teorias alterna
tivas da gravidade do ponto de vista do processo de fusão dos horizontes
de dois buracos negros. Numa primeira fase a gravidade escalar-tensor-vect
or é considerada. Começamos por apresentar um resumo da teoria\, seguido
da descrição da fusão\, feita com o traçar das trajectórias dos raio
s de luz que definem o horizonte de eventos.
Esta descrição ev
ita recorrer a grande poder computacional ao usar o método da razão extr
ema de massas\, no qual um dos buracos negros é considerado infinitamente
maior que o outro. Os parâmetros relevantes que descrevem a fusão são
então calculados\, designadamente a duração do processo\, a diferença
na área do horizonte pequeno\, e a taxa de crescimento da largura da garg
anta da fusão.
Após isto\, um estudo da gravidade cúbica Einst
einiana é levado a cabo. Como em gravidade escalar-tensor-vector\, um res
umo da teoria é apresentado\, seguido de uma descrição da fusão e dete
rminação dos parâmetros de fusão relevantes\, e é estabelecida a rela
ção entre o parâmetro de acoplamento no lagrangiano\, Õ\, e a intensid
ade dos efeitos gravíticos considerados. O estudo é extendido para regim
es do valor de Õ mais abrangentes do que aqueles contemplados até agora
na literatura.
Por fim\, após explorar os efeitos repulsivos do
buraco negro pequeno em ambas as teorias\, as condições que determinam o
comportamento atractivo e repulsivo em ambas as teorias são unificadas d
e maneira a serem aplicáveis à fusão de todos os buracos negros esferic
amente simétricos descritos por uma métrica semelhante à de Schwarzschi
ld.
Online
Resumo
Propomo-nos a analisar os parâmetros de poeira em supernov as do tipo Ia a partir de um conjunto de dados de 207 supernovas recolhido s pelo Dark Energy Survey (DES).
Propomo-nos
a criar uma metodologia de ajuste realizando primeiro testes com curvas de
luz de supernovas simuladas.
Fazem
os ajustes às curvas de luz dos dados do DES\, recolhendo valores de sBV
(stretch de cor)\, Bmax (magnitude na banda B no máximo)\, Tmax tempo de
máximo na banda B\, E(B-V) e Rv de cada uma das supernovas da base de dad
os. Descobrimos que Rv é um parâmetro difícil de constrangir com uso ex
clusivo de ajustes de dados.
Encont
ramos uma relação exponencial entre o Rv e o E(B-V) semelhante a relaç
ões encontradas na literatura\, embora não consigamos quantificá-la sat
isfatoriamente nos nossos dados com um ajuste linear nem com com um ajuste
exponencial.
Descobrimos que o Rv media
no dos nossos dados está abaixo do Rv mediano da Via Láctea e que a dist
ribuição de Av dos nossos dados segue uma exponencial\, novamente em con
cordância com estudos anteriores.
Comparamos os parâmetros de poeira das supernovas no nosso conjunto de da
dos com os parâmetros das suas galáxias de origem.
Encontramos evidências para a existência de múltiplas popul ações de Rv dentro do nosso conjunto de dados através de análise de di stribuições cumulativas. Os nossos resultados são consistentes com prev isões de variações de leis de extinção com a quantidade de extinção \, massa da galáxia de origem\, redshift e stretch.
Tentamos estimar Rv através de análise de populações
END:VEVENT BEGIN:VEVENT SUMMARY:Polarization patterns in the sky and their influence in astronomic al observations DTSTART:20221130T150000Z DTEND:20221130T170000Z DTSTAMP:20240329T082742Z UID:fa1b61d5-1545-48f4-bbba-056a7b74f753 SEQUENCE:1 CREATED:20221129T094355Z DESCRIPTION: Resumo:As condições perfeitas para uma observação astron ómica incluem um céu livre de contaminação luminosa. A contaminação luminosa é mais significatica em observações na banda do visível e pod e tornar-se uma fonte de erros sistemáticos em observações polarimétri cas. A Lua é o nosso objecto de estudo sendo a maior fonte de luz natural no céu noturno.De forma a compreender melhor como os padrões de polariz ação do céu devido a poluição luminosa afectam observações polarim étricas\, este projecto tem como objectivo compreender construir um model o que permita uma boa estimativa destes valores. O modelo considera a luz do luar que chega à atmosfera\, foi originalmente radiação solar reflet ida na luaa\, interage com as patículas atmosféricas e dispersa-se. Este fenómenos causa a padrões de polarização no céu que dependem princip almente da distância angular entre o alvo de observação e a Lua.Depende ndo da localização do observatório\, período e condições de observa ção\, o modelo estima as características de polarização do céu\, sim ulando os processos de dispersão com base na composição e densidade da atmosfera e comprimento de onda da luz incidente. Resultando na otimizaç ão de futuros planos de observação.Neste estudo\, dois modelos analíti cos são comparados. Adicionalmente\, com as observações feitas com o FO RS2 no observatório ESO-VLT no Paranal durante duas noites\, observa-se u ma excelente compatibilidade do modelo de Rayleigh com os dados observados . No entanto\, o modelo começa a falhar quando não há condições ideai s de observação e também para comprimentos de onda maiores. O modelo ba seado em dispersão múltipla e outras correções são necessários para obter resultados mais precisos em determinadas condições. Adicionalmente \, outras hipóteses foram tidas em consideração\, como a dependência d o comprimento de onda do grau de polarização ou do fator de despolariza ção.O modelo construído para os padões de polarização do céu noturn o ajudará a planear observações futuras e corrigir a polarização de f undo em observações palarimétricas que usem o VLT. LAST-MODIFIED:20221129T094355Z LOCATION:Anfiteatro QA\, Piso 1\, Pavilhão de Química - Campus da Alame da URL:http://df.vps.tecnico.ulisboa.pt/eventos/polarization-patterns-in-the- sky-and-their-influence-in-astronomical-observations/ X-ALT-DESC;FMTTYPE=text/html:
Resumo:
As condições pe
rfeitas para uma observação astronómica incluem um céu livre de contam
inação luminosa. A contaminação luminosa é mais significatica em obse
rvações na banda do visível e pode tornar-se uma fonte de erros sistem
áticos em observações polarimétricas. A Lua é o nosso objecto de estu
do sendo a maior fonte de luz natural no céu noturno.
De forma a compreender melhor como os padrões de pola
rização do céu devido a poluição luminosa afectam observações polar
imétricas\, este projecto tem como objectivo compreender construir um mod
elo que permita uma boa estimativa destes valores. O modelo considera a lu
z do luar que chega à atmosfera\, foi originalmente radiação solar refl
etida na luaa\, interage com as patículas atmosféricas e dispersa-se. Es
te fenómenos causa a padrões de polarização no céu que dependem princ
ipalmente da distância angular entre o alvo de observação e a Lua.
Dependendo da localização do observat
ório\, período e condições de observação\, o modelo estima as caract
erísticas de polarização do céu\, simulando os processos de dispersão
com base na composição e densidade da atmosfera e comprimento de onda d
a luz incidente. Resultando na otimização de futuros planos de observaç
ão.
Neste estudo\, dois modelos an
alíticos são comparados. Adicionalmente\, com as observações feitas co
m o FORS2 no observatório ESO-VLT no Paranal durante duas noites\, observ
a-se uma excelente compatibilidade do modelo de Rayleigh com os dados obse
rvados. No entanto\, o modelo começa a falhar quando não há condições
ideais de observação e também para comprimentos de onda maiores. O mod
elo baseado em dispersão múltipla e outras correções são necessários
para obter resultados mais precisos em determinadas condições.
Adicionalmente\, outras hipóteses foram tidas em consideração\, como
a dependência do comprimento de onda do grau de polarização ou do fator
de despolarização.
O modelo construído pa ra os padões de polarização do céu noturno ajudará a planear observa ções futuras e corrigir a polarização de fundo em observações palari métricas que usem o VLT.
END:VEVENT BEGIN:VEVENT SUMMARY:Improved gas transport of polyurethane-based membranes for blood oxygenation DTSTART:20221130T153000Z DTEND:20221130T170000Z DTSTAMP:20240329T082742Z UID:3d83fe66-cace-485f-a9b4-f4e675bf0c37 SEQUENCE:1 CREATED:20221128T151304Z DESCRIPTION: Extracorporeal Membrane Oxygenation (ECMO) is essential in cr itical care for themanagement of severe respiratory and cardiac failure. C onsidered the most importantpart of the ECMO circuit\, the membrane blood oxygenator (BO) is responsible formaintaining O2 and CO2 levels in the blo od. Current BOs require large membranesurface areas\, but these have poor hemocompatibility\, which leads to activation of thecoagulation system. De spite the considerable progress during the last decades incomponent techno logy and at the circuit level\, a BO capable of performing efficientlyin p rolonged ECMO does not exist. To improve the O2 permeability our research hasbeen focused on the development of new blend polyurethane-based (PUR)me mbranes\, using polyether and polyester-based segmented PURs\, which exhib itenhanced hemocompatibility\, in association with a good flex-life and me chanicalstrength.. LAST-MODIFIED:20221128T151304Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/improved-gas-transport-of-pol yurethane-based-membranes-for-blood-oxygenation/ X-ALT-DESC;FMTTYPE=text/html: Extracorporeal Mem
brane Oxygenation (ECMO) is essential in critical care for themanagement o
f severe respiratory and cardiac failure. Considered the most importantpar
t of the ECMO circuit\, the membrane blood oxygenator (BO) is responsible
formaintaining O2 and CO2 levels in the blood.
Current BOs requi
re large membranesurface areas\, but these have poor hemocompatibility\, w
hich leads to activation of thecoagulation system. Despite the considerabl
e progress during the last decades incomponent technology and at the circu
it level\, a BO capable of performing efficientlyin prolonged ECMO does no
t exist.
To improve the O2 permeability our research hasbeen foc
used on the development of new blend polyurethane-based (PUR)membranes\, u
sing polyether and polyester-based segmented PURs\, which exhibitenhanced
hemocompatibility\, in association with a good flex-life and mechanicalstr
ength..
Resumo
Nesta tese elabora mos um modelo numérico para prever o tempo e carga de sinais em detectore s de cintilador líquido de grande volume.
De
screvemos\, em particular para SNO+\, o fundamento físico da propagação
de luz em tais detectores e combinamos essa descrição com a discretiza
ção das variáveis físicas usadas para descrever o modelo. Para impleme
ntar o modelo computacionalmente\, várias optimizações\, incluindo apro
ximações\, são apresentadas e aplicadas ao algoritmo.
Os resultados em tempo e carga obtidos através dest
e modelo são comparados com resultados de referência obtidos com a simul
ação Monte Carlo usada na experiência SNO+\, e os resultados são discu
tidos no que toca à sua compatibilidade com os de referência e quanto à
sua capacidade para informar sobre ajustes do algoritmo de modelização
ou para optimizar o código. Um algoritmo de reconstrução baseado numa f
unção de verosimilhança é introduzido e adaptado tendo em conta as car
acterísticas dos resultados do modelo.
Finalmente\, sumarizamos as vantagens e desvantagens do modelo numér
ico e propomos formas de as aproveitar e contornar\, respectivamente. Disc
utimos também possibilidades de trabalho futuro na forma de melhorias ao
modelo e ajustes aos parâmetros utilizados.
Esta tese foca-se no caso particular do detector SNO+\, mas o mo delo pode ser aplicado prontamente a outros detectores de cintilação de grande volume. Optimizações que dependam da simetria esférica do detect or SNO+ não podem ser aplicadas directamente a outros detectores\, mas em tais casos outras simetrias\, frequentemente cúbicas\, existem e os mesm os métodos podem ser aplicados.
END:VEVENT BEGIN:VEVENT SUMMARY:Production of single-cycle laser pulses through nonlinear pulse co mpression DTSTART:20221130T160000Z DTEND:20221130T180000Z DTSTAMP:20240329T082742Z UID:21887558-8e12-4985-9d3e-ef40f617eeee SEQUENCE:2 CREATED:20221129T095009Z DESCRIPTION:Atualmente\, a maioria dos lasers ultracurtos são capazes de produzir impulsos com durações na ordem dos femtossegundos\, com recurso a osciladores de Ti:Sapphire.Estes impulsos ultracurtos são a ferramenta ideal para explorar a dinâmica dos eletrões em átomos\, sólidos e nan oestruturas. Como a resolução temporal está limitada pela duração do impulso\, alcançar impulsos mais curtos permite-nos explorar os processos inacessíveis até então. Estes impulsos podem existir na forma de impul sos isolados de atossegundos\, produzidos por lasers de impulsos com pouco s ciclos óticos num processo de geração de altas harmónicas\, permitin do assim o desenvolvimento de ferramentas de diagnóstico como difração de raios-x nos atossegundos ou espetrómetros de pequenas dimensões.Para obtermos impulsos laser de uma ou poucas oscilações\, criámos\, no labo ratório VOXEL (GoLP/IPFN\, Instituto Superior Técnico)\, um sistema de p ós-compressão. A nossa instalação consiste num laser comercial (40 fs\ , 800 nm\, 3mJ\, 1kHz) cujos impulsos são focados numa fibra oca com um d iâmetro interno de que está sujeita a uma pressão diferencial de Árgon . O impulso\, que à saída da fibra possui uma maior largura espetral\, é re-colimado antes de ser comprimido e analisado no tempo por um sistema D-Scan da empresa Sphere Ultrafast Photonics. Alguns mW de energia são a mostrados para compressão e análise. Atingimos impulsos com menos de 4 f s com pouca dispersão do atraso do grupo (GDD) e uma transmissão de 33%. Esta configuração constitui uma ferramenta poderosa para a geração de impulsos laser de um ciclo único no laboratório\, estando este agora eq uipado para produzir impulsos isolados de atossegundos com frequências na gama mais alta de ultravioletas através de um processo de geração de a ltas harmónicas.Fizemos também um estudo no Laboratoire d'\;Optique Apliquée (LOA)\, no Institut Polytechnique de Paris\, onde dois métodos estado-da-arte da pós-compressão foram estudados. Apresentamos também u ma conclusão sobre o método mais apropriado para cada situação. LAST-MODIFIED:20221129T095040Z LOCATION:Anfiteatro EA3\, Piso 1\, Torre Norte - Campus da Alameda URL:http://df.vps.tecnico.ulisboa.pt/eventos/production-of-single-cycle-la ser-pulses-through-nonlinear-pulse-compression/ X-ALT-DESC;FMTTYPE=text/html:Atualmente\, a maioria dos lasers ultracurtos são capazes de p
roduzir impulsos com durações na ordem dos femtossegundos\, com recurso
a osciladores de Ti:Sapphire.
Estes impulsos ultracurtos são a ferram
enta ideal para explorar a dinâmica dos eletrões em átomos\, sólidos e
nanoestruturas.
Como a resolução temporal está limitada pela
duração do impulso\, alcançar impulsos mais curtos permite-nos explora
r os processos inacessíveis até então. Estes impulsos podem existir na
forma de impulsos isolados de atossegundos\, produzidos por lasers de impu
lsos com poucos ciclos óticos num processo de geração de altas harmóni
cas\, permitindo assim o desenvolvimento de ferramentas de diagnóstico co
mo difração de raios-x nos atossegundos ou espetrómetros de pequenas di
mensões.
Para obtermos impulsos la
ser de uma ou poucas oscilações\, criámos\, no laboratório VOXEL (GoLP
/IPFN\, Instituto Superior Técnico)\, um sistema de pós-compressão. A n
ossa instalação consiste num laser comercial (40 fs\, 800 nm\, 3mJ\, 1kH
z) cujos impulsos são focados numa fibra oca com um diâmetro interno de
que está sujeita a uma pressão diferencial de Árgon. O impulso\, que à
saída da fibra possui uma maior largura espetral\, é re-colimado antes
de ser comprimido e analisado no tempo por um sistema D-Scan da empresa Sp
here Ultrafast Photonics.
Alguns mW de energia são amostrados p
ara compressão e análise. Atingimos impulsos com menos de 4 fs com pouca
dispersão do atraso do grupo (GDD) e uma transmissão de 33%. Esta confi
guração constitui uma ferramenta poderosa para a geração de impulsos l
aser de um ciclo único no laboratório\, estando este agora equipado para
produzir impulsos isolados de atossegundos com frequências na gama mais
alta de ultravioletas através de um processo de geração de altas harmó
nicas.
Fizemos também um estudo no Laboratoire d'\;Optique Apliquée (LOA)\, no Institut Polyt echnique de Paris\, onde dois métodos estado-da-arte da pós-compress ão foram estudados. Apresentamos também uma conclusão sobre o método m ais apropriado para cada situação.
END:VEVENT BEGIN:VEVENT SUMMARY:Looking for coherence effects in the Quark-Gluon Plasma DTSTART:20221130T170000Z DTEND:20221130T190000Z DTSTAMP:20240329T082742Z UID:414924b1-6d5d-4cb0-a5ee-d0b53843b254 SEQUENCE:1 CREATED:20221129T095412Z DESCRIPTION:ResumoO observável jet pull fornece informação relativament e ao fluxo de cor estabelecido entre dois jatos inter-conectados\, adicion almente à habitualmente obtida através do momento e do tamanho dos jatos . Apesar das correlações de cor já terem sido estudadas anteriormente\, propomo-nos desenvolver uma nova abordagem: aplicar o vetor jet pull em c oerência intra-jato. Para tal\, estudamos simulações de eventos protão -protão a energias de centro de massa semelhantes às do Large Hadron Col lider: √s=5 TeV e √s=13 TeV. Nestes eventos definimos singletos e octe tos de cor\, através do duplo decaimento fraco de bosões e de eventos QC D\, respetivamente. Definimos o observável pull angle num sistema di-jato formado através de técnicas de reconstrução anti-kT de jatos e de sub strutura de jatos. O objetivo consiste em testar se os sinais relacionados com coerência de cor se mantém em ambiente de colisões de iões pesado s. Ainda exploramos o decaimento do gluão num par c¯c\, através de mes ões D. Finalmente\, adicionamos um background térmico aos três sistemas \, tendo este características semelhantes às do background de uma colis ão Pb-Pb a √s=5.02 TeV. O background provoca alterações significativa s ao comportamento do singleto e do octeto c¯c. Dessa forma\, aplicamos u ma subtração de background ao nível dos constituintes\, semelhante à u tilizada nas experiências. Isto permite obter novamente a assinatura obti da em eventos pp em vácuo\, provando que os efeitos de coerência de cor podem ser testados em colisões de iões pesados. LAST-MODIFIED:20221129T095412Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/looking-for-coherence-effects -in-the-quark-gluon-plasma/ X-ALT-DESC;FMTTYPE=text/html:Resumo
O observável jet pull fornece informação relativamente
ao fluxo de cor estabelecido entre dois jatos inter-conectados\, adiciona
lmente à habitualmente obtida através do momento e do tamanho dos jatos.
Apesar das correlações de cor já terem sido estudadas anteriormente\,
propomo-nos desenvolver uma nova abordagem: aplicar o vetor jet pull em co
erência intra-jato. Para tal\, estudamos simulações de eventos protão-
protão a energias de centro de massa semelhantes às do Large Hadron Coll
ider: √s=5 TeV e √s=13 TeV.
Nestes eventos definimos singlet
os e octetos de cor\, através do duplo decaimento fraco de bosões e de e
ventos QCD\, respetivamente. Definimos o observável pull angle num sistem
a di-jato formado através de técnicas de reconstrução anti-kT de jatos
e de substrutura de jatos. O objetivo consiste em testar se os sinais rel
acionados com coerência de cor se mantém em ambiente de colisões de iõ
es pesados.
Ainda exploramos o decaimento do gluão num par c¯c
\, através de mesões D. Finalmente\, adicionamos um background térmico
aos três sistemas\, tendo este características semelhantes às do backgr
ound de uma colisão Pb-Pb a √s=5.02 TeV. O background provoca alteraç
ões significativas ao comportamento do singleto e do octeto c¯c.
Dessa forma\, aplicamos uma subtração de background ao nível dos con
stituintes\, semelhante à utilizada nas experiências. Isto permite obter
novamente a assinatura obtida em eventos pp em vácuo\, provando que os e
feitos de coerência de cor podem ser testados em colisões de iões pesad
os.
Resumo:
< p data-block-key="4s3hj">Os raios cósmicos de ultra-alta energia interage m com a atmosfera terrestre produzindo cascatas atmosféricas de alta ener gia\, cujos valores não são atingíveis nos aceleradores atuais\, como n o Large Hadron Collider (LHC). O número de muões na superfície da Terra é uma observável essencial para inferir a composição dos raios cósmi cos.Resumo:
Supercondutores de alta
temperatura (HTSc) podem conduzir densidades de corrente muito mais elevad
as que condutores convencionais\, sem as perdas associadas à resistência
elétrica. HTSc têm temperaturas críticas maiores que 77K\, que corresp
onde à temperatura de ebulição do azoto líquido à pressão ambiente.
Processos de arrefecimento que usam azoto líquido são menos caros e meno
s complexos que os processos que usam hélio líquido. Consequentemente\,
HTSc são altamente vantajosos quando comparados com supercondutores conve
ncionais para aplicações tecnológicas. Modelar sistemas com HTSc é ess
encial.
Atualmente\, os modelos usados baseiam-se numa lei de po
tências para a caraterística E-J. Esta lei é baseada em observações e
xperimentais e é uma aproximação ao Modelo de Estado Crítico de Bean.
A altamente não linear relação E-J resulta\, por vezes\, em computaçõ
es numericamente instáveis e lentas. Neste trabalho\, apresentamos um mod
elo para blocos de HTSc\, o modelo densidade\, que é derivável da teoria
fenomenológica de Ginsburg-Landau para a supercondutividade.
E
ste trabalho é desenvolvido sob a permissa de que a constante de Ginsburg
-Landau tem um valor elevado e\, também\, sob a permissa de que a magnitu
de do campo magnético aplicado é elevada o suficiente para que a distân
cia entre as linhas de fluxo seja muito menor que o comprimento de penetra
ção\, permitindo\, assim\, usar um modelo de campo médio. Para sistemas
de YBCO e GdBCO com duas dimensões\, as distribuições de campo magnét
ico dentro dos blocos para os dois modelos estão em concordância na maio
ria dos casos.
O modelo baseado na lei das potências tem sempre
tempos de computação menores. No entanto\, as simulações que usam o m
odelo da densidade apresentam sempre convergência e o mesmo não acontece
para o modelo da lei das potências. Vários parâmetros são necessário
s para definir totalmente o modelo da densidade.
O comprimento d
e coerência o comprimento de penetração e a constante de relaxação te
mporal são determinados por teorias microscópicas. Outros parâmetros\,
como a densidade de corrente de nucleação\, são escolhidos heuristicame
nte. Estudámos o efeito de variar esses parâmetros nas distribuições f
inais de campo magnético.
Resumo da tese:< /b>
A distribuição quântica de chaves (QKD
) explora os princípios da mecânica quântica para gerar e distribuir ch
aves privadas usando sistemas quânticos e um canal clássico público aut
enticado. Apesar de ser incondicionalmente segura\, as suas implementaçõ
es normalmente não o são devido a fontes de fuga de informação inesper
adas\, chamadas canais laterais. Espiões exploram estes canais laterais p
ara obter informação sobre a chave privada.
Canais laterais em
QKD ou são semelhantes aos encontrados em implementações clássicas ou
estão relacionados com o processamento quântico. Até agora\, a investi
gação e o desenvolvimento na área têm vindo a negligenciar os primeiro
s.
Nesta tese\, revemos sumariament
e os principais avanços na análise de segurança de QKD\, os principais
componentes das implementações e algoritmos de pós-processamento cláss
ico e o uso de repetidores para aumentar a distância de transmissão. Tam
bém revemos de forma integral os principais ataques de canal lateral a im
plementações de QKD e as suas contramedidas.
Propomos também um ataque de canal lateral clássico à etapa
de amplificação de privacidade dum protocolo geral de QKD\, usando téc
nicas de aprendizagem automática para analisar o seu consumo elétrico. A
nalisamos vários cenários simulados e conseguimos recuperar toda a chave
privada múltiplas vezes. A máquina de gradient boosting foi o modelo co
m melhor performance em praticamente todos os cenários e recuperou toda a
chave para taxas de amostragem do instrumento de medida suficientemente a
ltas\, independentemente do tamanho da matriz de hashing e do nível de ru
ído usados.
Para modelos imperfeitos\, formulamos uma estratég
ia\, baseada na análise das matrizes de confusão do modelo\, que pode vi
abilizar uma procura da chave por força bruta. Nas nossas abordagens de a
taque\, encontramos um trade-off entre o poder computacional necessário e
a performance do ataque. Também discutimos contramedidas baseadas em ins
erção de ruído\, masking e randomização. Algumas delas conseguem rest
aurar a segurança incondicional do protocolo de QKD.
Este trabalho demonstra que técnicas de aprendizagem a utomática podem ser usadas para caraterizar canais laterais duma implemen tação de QKD de forma robusta e executar ataques poderosos.
END:VEVENT BEGIN:VEVENT SUMMARY:Topological waves in two-dimensional plasmas DTSTART:20221205T160000Z DTEND:20221205T180000Z DTSTAMP:20240329T082742Z UID:fb74bbcf-fb5d-40b1-9122-a601fc626b55 SEQUENCE:1 CREATED:20221202T152126Z DESCRIPTION: Abstract In this work we compactify plasmas with two differ ent types of electric fields applied and then find edge waves at the inter face between magnetized domains.The first case is a local interaction caus ed by a Field-Effect Transistor\; a second case\, without a FET\, with non -local Coulomb interactions stemming from all electronic density in the fl uid is also addressed.Two distinct edge-modes are calculated for each case \, their dispersion relation and velocity profiles.All four edge-modes are simulated in magnetized graphene with a hydrodynamic simulator. LAST-MODIFIED:20221202T152126Z LOCATION:Sala de Formação Avançada do DF (Sala 2-8.11 - 2º Piso do Pav ilhão de Física) URL:http://df.vps.tecnico.ulisboa.pt/eventos/topological-waves-in-two-dime nsional-plasmas/ X-ALT-DESC;FMTTYPE=text/html:Abstract
In this work we compactify plasmas with two different types of electric fields applied and then find edge waves at the interface between magnetized domains.
The fi rst case is a local interaction caused by a Field-Effect Transistor\; a se cond case\, without a FET\, with non-local Coulomb interactions stemming f rom all electronic density in the fluid is also addressed.
Two distinct edge-modes are calculated for each case\, their dispersion relation and velocity profiles.
A ll four edge-modes are simulated in magnetized graphene with a hydrodynami c simulator.
END:VEVENT BEGIN:VEVENT SUMMARY:Accretion disks around compact objects DTSTART:20221206T100000Z DTEND:20221206T120000Z DTSTAMP:20240329T082742Z UID:114d6117-ca7c-485b-99f3-baa1a55bfa57 SEQUENCE:1 CREATED:20221205T095826Z DESCRIPTION: Resumo:Um dos maiores desafios que enfrentamos em astrofísi ca é estudar buracos negros e compreender de que forma a relatividade ger al os decreve adequadamente. Acredita-se que os candidatos a buracos negro s sejam bem descritos pela solução de Kerr. Contudo\, a evidenciência d e matéria escura e o comportamento anómalo da gravidade no interior do h orizonte de eventos levam-nos a considerar outras soluções de espaço-te mpo conhecidas como \\textit{black hole mimickers}. Algumas teorias sugere m que campos escalares bosónicos podem formar soluções compatas estáve is\, dificeis de distinguir observavelmente de buracos negros\, intitulada s de estrelas dea bosões. Neste projeto\, consideramos o seu limite para campos fracos\, isto é\, campos escalares muito leves ($\\sim 10^{-17}eV$ ) acoplados de forma fraca com a gravidade\, conhecido como estrela de bos ões Newtoniana. O nosso objetivo é estudar se estas soluções podem rep roduzir a acreção de um buraco negro de Kerr\, sendo potenciais \\textit {black hole mimickers}. Aplicando o modelo de Novikov-Thorne\, descrevemos a acreção de um disco estacionário\, fino\, e opticamente denso. Compa ramos o fluxo eletromagnético de discos em torno de buracos negros e de e strelas de bosões newtonianas\, identificando assinaturas sobre a naturez a do objecto acretante. Encontramos um espaço de parâmetros de massa e r otação do buraco negro tal que a luminosidade bolométrica dos discos é a mesma. Discutimos como o espectro de emissão dos discos na banda mais energética do ultravioleta pode ser usado para diferenciar as duas soluç ões de espaço-tempo. Por fim\, verificamos se estrelas de bosões newton ianas descrevem as luminosidades de alguns centros galáticos ativos. Conc luimos que estes que são consistentes com soluções compactas de campos escalares leves ($\\sim 10^{-16} - 10^{-19} eV$). LAST-MODIFIED:20221205T095826Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/accretion-disks-around-compac t-objects/ X-ALT-DESC;FMTTYPE=text/html:
Resumo:
Um dos maiores de
safios que enfrentamos em astrofísica é estudar buracos negros e compree
nder de que forma a relatividade geral os decreve adequadamente. Acredita-
se que os candidatos a buracos negros sejam bem descritos pela solução d
e Kerr. Contudo\, a evidenciência de matéria escura e o comportamento an
ómalo da gravidade no interior do horizonte de eventos levam-nos a consid
erar outras soluções de espaço-tempo conhecidas como \\textit{black hol
e mimickers}.
Algumas teorias sugerem que campos escalares bosó
nicos podem formar soluções compatas estáveis\, dificeis de distinguir
observavelmente de buracos negros\, intituladas de estrelas dea bosões. N
este projeto\, consideramos o seu limite para campos fracos\, isto é\, ca
mpos escalares muito leves ($\\sim 10^{-17}eV$) acoplados de forma fraca c
om a gravidade\, conhecido como estrela de bosões Newtoniana. O nosso obj
etivo é estudar se estas soluções podem reproduzir a acreção de um bu
raco negro de Kerr\, sendo potenciais \\textit{black hole mimickers}.
Aplicando o modelo de Novikov-Thorne\, descrevemos a acreção de um
disco estacionário\, fino\, e opticamente denso. Comparamos o fluxo elet
romagnético de discos em torno de buracos negros e de estrelas de bosões
newtonianas\, identificando assinaturas sobre a natureza do objecto acret
ante. Encontramos um espaço de parâmetros de massa e rotação do buraco
negro tal que a luminosidade bolométrica dos discos é a mesma.
Discutimos como o espectro de emissão dos discos na banda mais energét
ica do ultravioleta pode ser usado para diferenciar as duas soluções de
espaço-tempo. Por fim\, verificamos se estrelas de bosões newtonianas de
screvem as luminosidades de alguns centros galáticos ativos. Concluimos q
ue estes que são consistentes com soluções compactas de campos escalare
s leves ($\\sim 10^{-16} - 10^{-19} eV$).
Desenvolvemos um modelo hidrodinâmico para o escoamento de q
uasi-partículas em grafeno bicamada no ponto de neutralidade\, o qual imp
lementamos numericamente acoplando a equação de Poisson. A partir do mod
elo teórico\, caracterizamos a instabilidade de duas correntes eletrão-b
uraco quanto ao efeito da temperatura\, velocidade inicial de deriva\, cam
po magnético e colisões.
Comprova
mos a existência de um limiar de velocidade de deriva para criar instabil
idades da ordem da velocidade térmica e uma velocidade de pico\, após a
qual a taxa de crescimento máxima satura. Neste estágio\, o vetor de ond
a mais instável adquire uma componente perpendicular à velocidade inicia
l. Tanto a contribuição de um campo magnético externo como das colisõe
s diminuem a taxa de crescimento\, mas\, sob parâmetros típicos\, o seu
papel só se torna aparente para modos de comprimento de onda muito longos
.
Confirma-se a possibilidade de re
laxar a corrente somente através de mecanismos eletrostáticos no limite
isotérmico\, dando origem a uma condutividade longitudinal DC bem definid
a ∝T³/². Incluindo o espalhamento\, dois regimes de transporte distint
os\, dominados respectivamente por processos eletrostáticos e colisões\,
são delimitados pela temperatura e pelo campo elétrico. A mesma anális
e da condutividade Hall revelou que as diferenças relativas ao regime lin
ear não são tão marcantes.
Finalmente\, a inclusão do efeito
do aquecimento Joule inibe o estabelecimento de um regime de saturação
excluindo o espalhamento\, e a adição desses termos\, juntamente com a d
issipação de calor pelos fonões para contrabalançar a potência dissip
ada por efeito de Joule\, resulta num comportamento significativamente dif
erente da condutividade com a temperature
As células solar
es CIGS são um candidato promissor para aplicações como fonte de energi
a em ambientes de radiação severa\, devido à sua elevada eficiência de
conversão e capacidade para manter níveis de rendimento adequados após
sofrer danos induzidos pela radiação. Este trabalho pretendeu testar a
resistência das células CIGS à radiação monitorizando os efeitos da i
rradiação com protões nas suas propriedades elétricas e estruturais e
avaliando o impacto de tratamentos por aplicação de luz e corrente na re
cuperação de dispositivos irradiados.
A caracterização J-V
com luz após irradiação com protões de 1 MeV evidenciou a tendên
cia de degradação do rendimento das células solares com fluências apli
cadas desde 3.8×1012 H+/cm2 até 3.8×1013 H+/cm2\, sendo que a redução
da eficiência foi dominada por perdas na voltagem de circuito aberto. As
medidas J-V no escuro revelaram um aumento da densidade de corrent
e de saturação e do fator de idealidade após a irradiação com fluênc
ias até 1×1014 H+/cm2\, o que sugere que os danos provocados pela radia
ção introduziram defeitos no absorvedor CIGS que promovem recombinação
do tipo Shockley-Read-Hall na região de espaço-carga e/ou nas fronteira
s dos grãos.
Durante um período de repouso no escuro e à temp
eratura ambiente\, nenhuma recuperação significativa desses defeitos foi
observada. Adicionalmente\, medidas de difração de raios-X de ângulo r
asante feitas em amostras virgens e irradiadas não mostraram quaisquer si
nais de degradação da qualidade cristalina após a irradiação com prot
ões.
As metastabilidades observadas nas células CIGS aquando do
s tratamentos por aplicação de luz e corrente foram interpretadas como s
endo um fenómeno de fotocondutividade persistente que melhorou temporaria
mente as propriedades de recombinação em dispositivos virgens e irradiad
os. Ambos os tratamentos contribuíram\, no longo prazo\, para uma recuper
ação parcial das propriedades elétricas em dispositivos previamente irr
adiados.
Resumo: p>
Plasmas eletrão-positrão existem na vizinhan
ça de objetos astrofísicos\, como estrelas de neutrões. Este é um dos
motivos que contribui para o interesse geral em estudar os comportamentos
destes plasmas\, que contrastam fortemente com plasmas de laboratório con
vencionais ião-eletrão devido à simetria das massas entres as espécies
positivas e negativas. A produção de pares eletrão-positrão em quanti
dade suficiente para observar efeitos coletivos é um desafio em física m
oderna. Uma maneira de gerar estes pares consiste em colidir um impulso de
laser de alta intensidade com um feixe de eletrões relativista.
Este esquema permite a produção de fotões de alta energia através da
dispersão de Compton não linear\, que posteriormente decaem num par ele
trão-positrão através da criação de pares de Breit-Wheeler não linea
r. Uma desvantagem destas experiências atualmente reside no número baixo
de positrões produzidos e na interferência com outros processos (como p
ares produzidos por fotões de bremsstrahlung).
Nesta tese\, um
esquema usando um impulso de laser com duas cores é usado para alcançar
a separação espacial dos pares produzidos na interação\, e dos eletrõ
es do feixe inicial. Um modelo teórico é introduzido para prever quando
ocorre separação de momento das cargas em função dos parâmetros do im
pulso de duas cores (especialmente\, da fase) e simulações Partícula-na
-Célula mostram que este efeito dá origem a observáveis mensuráveis em
experiências futuras.
Simulações com largura de feixe finito
mostram a separação física dos pares e a corrente produzida pelo movim
ento destas\, que pode ser controlado variando a fase relativa entre as du
as componentes do laser.
Axiões são part
ículas hipotéticas que surgiram como solução para o problema de CP da
CDQ\, porém o seu potencial como partículas de matéria escura logo foi
descoberto. Uma das possíveis formas de produção destas partículas é
através do acoplamento com fotões sob a influência de campos eletromagn
éticos intensos\, tais como os que existem no núcleo das estrelas.
Neste trabalho\, exploramos este canal de perda de energia em estrela
s massivas\, nas quais é esperado um efeito mais significativo. Mais espe
cificamente\, calibramos a supergigante vermelha ɑ-Orionis\, tendo em con
ta diferentes valores da constante que rege o acoplamento acima mencionado
\, com o objetivo de estabelecer um limite superior na mesma\, tendo por b
ase os efeitos desta interação na estrutura e evolução da estrela.
Com base nesta análise\, concluímos que a adição de perdas de e
nergia associadas aos axiões dá origem a perfis distintos daqueles que n
ão incluem matéria escura\, especialmente nas regiões mais centrais\, p
ara as quais ondas de gravidade internas -- possivelmente detetadas no fut
uro -- devem configurar um bom diagnóstico. Finalmente\, estabelecemos um
limite superior na constante de acoplamento de a partir do qual não e
ncontramos modelos capazes de reproduzir as características da Betelgeuse
.
Resumo:
< p data-block-key="5p89g">O h-BN é um semicondutor de hiato largo e mergente. A sua excelente condutividade térmica\, resistência mecânica e resistência à oxidação\, aliadas à sua estrutura em camadas semelha nte à da grafite tornam-no num material promissor para aplicações em na noeletrónica bidimensional.Resumo:
Neste trabalho politopos de Bell e correlações
quânticas foram estudadas para Distribuição de Chaves Quânticas de mo
do Semi-independente de Dispositivos (DCQ SID). Para atingir este objetivo
\, diferentes politopos de Bell foram explorados para encontrar novas desi
gualdades de Bell que demonstram potencial para comunicações quânticas.
Neste trabalho é apresentada uma descrição por facets comple
ta pela primeira vez dos politopos (6\,3\,2\,2)\, (3\,3\,3\,2) e (3\,2\,3\
,3) e uma descrição incompleta dos politopos (2\,2\,4\,4)\, (3\,3\,2\,4)
e (4\,3\,3\,2). Para cada desigualdade gerada\, certas propriedades de in
teresse foram estudadas nomeadamente o limite quântico\, a eficiência m
ínima para fechar a Lacuna da Deteção e uma estimativa da dimensão mí
nima necessária para atingir o limite quântico.
A utilidade de
stas desigualdades para DCQ foi explorada assumindo que os estados quânti
cos partilhados entre a Alice\, o Bob e a Eve têm uma dimensão máxima d
e d=4x4x4. Das desigualdades estudadas\, I22441 e I[[2\,2\,3\,3]\,[2\,2\,2
]]2 demonstram os melhores resultados.
Para I22441 a eficiência
mínima para obter chaves secretas foi ηQKD = 0.920 e a taxa máxima de
chaves secretas foi 1.979. Para I[[2\,2\,3\,3]\,[2\,2\,2]]2 a eficiência
mínima para obter chaves secretas foi ηQKD =0.912 e a taxa máxima de c
haves secretas foi 1.284.
Resumo:
Devido ao aumento da resistência antimicrobian
a\, o campo das vacinas bacterianas está a ter um grande desenvolvimento
recentemente.
O aumento da potência e eficiência do computador
es aumentou a utilização de modelos computacionais para a sua investiga
ção. Para este projecto\, será implementada uma metodologia para realiz
ar simulações molecularas cromatográficas de troca iónica para lisozim
a\, uma proteína conhecida na literature\, e sepharose FF como a r
esina\, para comparar parâmetros de interacção utilizando o formalismo
de steric mass action. Isto será realizado pelo grupo de Downstrea
m processing na Janssen Vaccines em estreita coordenação com os engenhei
ros da empresa de software de simulacoes moleculares Schrodinger.
Em primeiro lugar\, foram feitas simulações de 50 ns para 32 orientaç
ões da proteína. A fim de determinar quais destas estabilizaram ou ating
iram o equilíbrio e depois podem ser utilizadas para avançar a fim de at
ingir o objectivo\, os dados da simulação foram primeiro examinados util
izando a energia de interacção proteína-superfície e a distância do c
entro da massa\, a partir daí algumas das orientações foram removidas.<
br/>
Finalmente\, foram criados mapas de distância para estimar os do
is parâmetros de steric mass action: characteristic charge
e steric hindrance factor para todas as restantes orientações\, u
tilizando duas distâncias de corte para verificar a dependência da mesma
. Os valores de characteristic charge obtidos foram 1.14±0.62 e 2.
64±1.32\, e os valores de steric hindrance factor foram 48.91±9.3
0 e 48.42±7.81. Os resultados e uma estratégia para obter a constante de
equilíbrio foram discutidos em detalhe.
Resumo:
< p data-block-key="331ie">Conseguem ser avistadas no horizonte as vantagens prometidas por computação quântica. No entanto\, essas vantagens são mantidas longe devido a obstáculos como o ruído e a decoerência. Esses obstáculos limitam severamente a escalabilidade de computadores quântico s\, mas uma das maneiras de enfrentar o problema poderá ser através da d istribuição da computação quântica onde\, idealmente\, poderíamos au mentar os recursos computacionais apenas adicionando nodos ao cluster de c omputadores quânticos. Neste projecto é proposto um novo método para di stribuir quantum annealing. The aim of the tal
k is to introduce some notions of higher gauge theory for a physics audien
ce. Higher gauge theory is a generalization of standard gauge theory\, whe
re everything is raised one (or more) dimensions\, e.g. the gauge potentia
ls become anti-symmetric 2-index tensors\, and the field strengths become
antisymmetric 3-index tensors.
The geometric language of differen
tial forms provides a useful framework for describing higher gauge theory.
The connections in the title refer both to the mathematical term for gaug
e potentials and to links with notions more familiar to physicists\, such
as monopoles\, the standard model\, Wilson loops etc.
Resumo:
< p data-block-key="eebkn">Apesar dos seus vários sucessos\, o Modelo Padr ão de física de partículas deixa alguns problemas em aberto\, nomeadame nte a origem da assimetria bariónica do Universo e oscilações de neutri nos. Sabe-se por isso que a teoria está incompleta.Resumo
< p data-block-key="dct2">O mundo está longe de atingir os objetivos da Age nda 2030 para o Desenvolvimento Sustentável. O setor de energia é respon sável por quase três quartos das emissões que causam as alterações cl imáticas\, provando que\, para atingir estes objetivos\, é necessário i mplementar novas soluções neste setor.Mappings between li quid crystals and superconductors motivated interest on the effects of chi ral molecules on the spin transport across aconducting electronic system a nd on the possible influence of topological states.Theinterplay between an incommensurate potential andtopological states is alsodiscussed\, in the context ofa superconductor.
END:VEVENT BEGIN:VEVENT SUMMARY:Using numerical relativity to search for physics beyond the Standa rd Model in gravitationalwave observations: high-mass LIGO-Virgo events as boson-star mergers DTSTART:20221215T143000Z DTEND:20221215T160000Z DTSTAMP:20240329T082742Z UID:1b43b8b5-1c33-4b80-84f3-8748f77a3e71 SEQUENCE:1 CREATED:20221129T153724Z DESCRIPTION: ABSTRACT: Gravitational-wave astronomy has delivered dramatic leaps forward in our understanding of gravity\, astrophysics and our Univ erse at large. Despite this success\, we are yet to find evidence for one of the holy grails for current scientific research: physics beyond General Relativity (GR) and Standard Model of Particle Physics (SM). To this end\ , ultra-light bosons are not only one of the simplest extensions of the SM but are also widely considered good candidates to build up part of Dark M atter. For this reason\, important efforts are being dedicated towards sea rching for these particles and\, specifically\, for the impact of boson cl ouds on black-holes. In this talk I will discuss an alternative strategy t o look for these particles. In particular\, I will present the first syste matic comparison\, within the framework of Bayesian inference\, of LIGO-Vi rgo events to a signal model for a specific type of object beyond the SM\, namely a set of nearly 1000 numerical simulations of mergers of exotic ob jects known as (vector) boson-stars: self-gravitating condensates of ultra light bosons. I will discuss the chances that a fraction of the underlying population of these events correspond to boson-star mergers instead of bl ack-hole ones\, providing estimates of the mass of the corresponding ultra light boson. If time permits\, I will also discuss the effect of the quant um properties of boson-stars in their gravitational emission and the conse quence of its inclusion in parameter inference and model selection. LAST-MODIFIED:20221129T153724Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/using-numerical-relativity-to -search-for-physics-beyond-the-standard-model-in-gravitationalwave-observa tions-high-mass-ligo-virgo-events-as-boson-star-mergers/ X-ALT-DESC;FMTTYPE=text/html: ABSTRACT:
Gra
vitational-wave astronomy has delivered dramatic leaps forward in our unde
rstanding of gravity\, astrophysics and our Universe at large. Despite thi
s success\, we are yet to find evidence for one of the holy grails for cur
rent scientific research: physics beyond General Relativity (GR) and Stand
ard Model of Particle Physics (SM). To this end\, ultra-light bosons are n
ot only one of the simplest extensions of the SM but are also widely consi
dered good candidates to build up part of Dark Matter.
For this
reason\, important efforts are being dedicated towards searching for these
particles and\, specifically\, for the impact of boson clouds on black-ho
les. In this talk I will discuss an alternative strategy to look for these
particles. In particular\, I will present the first systematic comparison
\, within the framework of Bayesian inference\, of LIGO-Virgo events to a
signal model for a specific type of object beyond the SM\, namely a set of
nearly 1000 numerical simulations of mergers of exotic objects known as (
vector) boson-stars: self-gravitating condensates of ultralight bosons.
I will discuss the chances that a fraction of the underlying popul
ation of these events correspond to boson-star mergers instead of black-ho
le ones\, providing estimates of the mass of the corresponding ultralight
boson. If time permits\, I will also discuss the effect of the quantum pro
perties of boson-stars in their gravitational emission and the consequence
of its inclusion in parameter inference and model selection.
Abstract:
Extreme Ultraviolet radiation (EUV) from high harmonic generation (HHG)
results in ultrashort coherent pulses of 10'\;s nm wavelength. Their d
uration\, down to the attosecond range\, allows probing ultrafast processe
s\, while their degree of coherence at short wavelength allows coherent di
ffractive imaging techniques to be implemented with resolutions reaching t
he wavelength range. However\, due to low reflectivity and being highly ab
sorbed by most materials\, there'\;s still the need to improve EUV ima
ging methods.
In this work\, we explored novel EUV HHG Imaging te
chniques\, including the characterization of Lithium Fluoride detectors\,
generation of vortex beams and imaging with Spiral Zone Plates\, a very pr
omising phase contrast method.
Abstract:
Quantum computers are a promising tool to solve certain problems that ar
e out of reach of classical computers. In this presentation\, I propose ne
w quantum algorithms for solving some nonlinear partial differential equat
ions\, which occur frequently in the context of plasma physics.
I start by presenting new classical methods with better asymptotic complex
ity\, and then prove that\, when compared with the classical case\, this n
ew quantum algorithm shows an exponential speedup with regards to the numb
er of time steps considered\, while also having a quadratic speedup in oth
er parameters. Additionally\, I also propose a new techniques to perform q
uantum error correction and to study quantum many-body systems.
Abstract:
Quantum computing enjoys some proven computational advantage over classi
cal computers\, with alluring applications: e.g.\, quantum system simulati
on\, quantum chemistry\, cryptography\, machine learning.
Howeve
r\, current implementations of quantum computers are still far from resili
ent to effects such as dephasing and decoherence\, putting them in stark c
ontrast to the classical computing technology developed over the last cent
ury. We would like to make use of both these aspects (quantum computationa
l power and classical computing technology)\, thus motivating the seek for
hybrid algorithms: those that combine the two types of computation.
<
br/> But\, this raises the question: when limiting\, for example\, the max
imum coherent depth to the quantum circuits used\, is any quantum advantag
e preserved? If so\, how much\, and in to what relation to the limits impo
sed? We analyze this question from a more tractable perspective\, namely\,
by modelling such a limitation as a limitation on the number of calls mad
e coherently to an oracle of the problem.
We establish an interp
olation regime for a particular problem (that of Eigenvalue Estimation) as
a generalization of existing results in the literature\,and by applying a
recently developed technique\, named Quantum Singular Value Transformatio
n. We then look at prospective following results\, by inspecting the class
es of problems for which the maximum quantum speedup is known (but an inte
rpolating regime is not).
Resumo
< p data-block-key="7v9p6">Informação é um dos recursos mais valiosos do mundo e a informação quântica visa trazer um novo paradigma. Um dos ing redientes essenciais para as tecnologias de fotónica quântica\, em parti cular comunicações quânticas seguras\, são fontes de pares de fotões entrelaçados. O entrelaçamento quântico é uma propriedade particular d os sistemas quânticos que permite a implementação de comunicações seg uras que de outra forma seriam impossíveis com informação clássica.Abstract: Quantum M atter commonly refers to materials which require quantum mechanics for a p roper description\, and its study falls mainly in the field of condensed m atter. Motivated by the interdisciplinarity in the most recent challenges of modern physics – namely topology\, plasmonics\, quantum technologies and dark matter – quantum matter requires different tools and covers sub jects of various disciplines: plasma physics\, material science and partic le physics. This is why the best theoretical physics institutes across the world strongly invest on quantum matter research.
In this talk\, I will explain my resea rch in quantum matter\, which\, in a nutshell\, comprises the study of qua ntum materials under the view of a plasma physicist (and vice versa). In p articular\, I will present three axes of research that put in evidence suc h a rich\, interdisciplinary merging of disciplines: graphene plasmonics\, production and detection of axions (one of the best candidates to dark ma tter) in plasmas and meta-materials\, and quantum simulations with cold at oms. I will conclude with a consideration on how my theoretical work is in close relation to the experiments performed both at IST and in other inst itutions.
END:VEVENT BEGIN:VEVENT SUMMARY:The Thermodynamics of Quantum Computers DTSTART:20230118T143000Z DTEND:20230118T160000Z DTSTAMP:20240329T082742Z UID:209bde61-a8f8-47a1-8eef-b4b07bd8711f SEQUENCE:1 CREATED:20230103T093202Z DESCRIPTION: Exploiting quantum dynamics and quantum correlations to proce ss information has established new forms of computation and simulation\, o ffering significant speed-ups in the time of the computations. However\, a nother potential advantage of quantum dynamics\, still poorly explored\, i s the energetic performance of the computations\, currently a bottleneck i n classical high-performance computing. In this seminar\, I will discuss s ome recent results we have obtained in the study of the thermodynamics of quantum gates\, a physics of information problem currently getting increas ing attention. LAST-MODIFIED:20230103T093202Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/the-thermodynamics-of-quantum -computers/ X-ALT-DESC;FMTTYPE=text/html: Exploiting quantum
dynamics and quantum correlations to process information has established
new forms of computation and simulation\, offering significant speed-ups i
n the time of the computations.
However\, another potential adva
ntage of quantum dynamics\, still poorly explored\, is the energetic perfo
rmance of the computations\, currently a bottleneck in classical high-perf
ormance computing. In this seminar\, I will discuss some recent results we
have obtained in the study of the thermodynamics of quantum gates\, a phy
sics of information problem currently getting increasing attention.
ABSTRACT: Ultra-rel
ativistic collisions of black holes are ideal settings where to investigat
e how general relativity behaves under extreme conditions. A large fractio
n of the allowed parameter space has been explored over the past 13 years
(including mass\, spin\, impact parameter)\, with the notable exception of
charge.
The inclusion of charge is significant because it adds
non trivial degrees of freedom to the system. For example\, charge constit
utes another way to reach extremality (together with spin) and opens up a
new channel to radiate away energy (through electromagnetic waves). Moreov
er\, charge makes the study more directly relevant to particle physics and
the production of microscopic black holes in cosmic rays and in particle
accelerators.
In this talk\, I am going to present the first num
erical-relativity simulations of head-on collisions of black holes with th
e same charge and mass. In particular\, I am going to discuss what they ca
n teach us about a variety of conjectures\, including cosmic censorship an
d the role of the inner structure of bodies colliding at relativistic spee
d.
Many extreme astrophysical scenarios share common underlying m
icrophysics with laboratory scenarios with relativistic particle beams and
ultra-intense lasers. In these conditions\, collective plasma effects dri
ven by relativistic flows\, ultra-high field intensities\, and quantum ele
ctrodynamics effects are intertwined.
In many scenarios\, these
relativistic and quantum effects can have direct consequences on the colle
ctive plasma dynamics. The underlying first principle mechanisms are highl
y nonlinear\, and occur at scales far from the plasma or the object scales
\, making these processes intrinsically multi-scale\, and thus requiring a
combination of theory and large-scale numerical simulations.
Th
e conditions under which extreme plasma physics can be relevant will be di
scussed\, along with the recent progress (from large-scale simulations of
compact objects to multi-dimensional laser/beam plasma interactions)\, ill
ustrating how ultra-intense electromagnetic fields approaching the critica
l Schwinger field impact the collective plasma dynamics. This interplay wi
ll be emphasized\, and the main challenges and open questions will be pres
ented.
Work partially supported by the Europea n Research Council (AdG InPairs).
END:VEVENT BEGIN:VEVENT SUMMARY:Particle Physics Seminars I DTSTART:20230125T160000Z DTEND:20230125T190000Z DTSTAMP:20240329T082742Z UID:37797a1c-f514-470f-9a3d-71ce28d7033d SEQUENCE:6 CREATED:20221223T115238Z DESCRIPTION:Speaker: Liliana ApolinárioTitle: Unveiling the time structur e of QCD jetsAbstract: Heavy-ion collisions are a unique laboratory to rec reate the high energy and density conditions prevalent during the primordi al moments of our Universe: the Quark-Gluon Plasma (QGP). This new state o f matter is made of the elementary building blocks (quarks and gluons) of Quantum Chromodynamics (QCD)\, a key ingredient of the Particle Physics St andard Model. Unveiling the characteristics of the QGP allows us to ascert ain the QCD'\;s fundamental properties. This goal can be achieved in h adronic collisions through jets: spray of particles that result from the f ragmentation of high-energy quarks and gluons produced concurrently with t he collision. The fact that jets in proton-proton collisions are well unde rstood has allowed us to successfully use them to extract the QGP'\;s time-averaged properties. However\, jets are evolving multi-scale objects that witness the entire space-time evolution of the system\, making them u nique tools for analysing the strong time dependence of the QGP properties . In this talk\, I will present the most recent breakthroughs that unlocke d time-differential methods for a full time-scan of the QGP at current col liders'\; energies.Speaker: Nuno LeonardoTitle: The LHC at the intensi ty frontierAbstract: The LHC is our most powerful tool to probe nature at the smallest scales and most fundamental level. The strategy is to accumul ate large datasets at high energies to search for tiny signals. One such s ignal was revealed a decade ago\, and resulted in the experimental confirm ation of the last standard model particle. While no new particles beyond t he standard model have been established so far\, there is tantalising evid ence of their presence in the data. Namely\, a persistent and significant pattern of deviations from the theory predictions has been revealed\, the so-called flavour anomalies. I’ll present the exploration of rare signal s around the flavour sector that we’ll continue to pursue at the LHC and beyond. Such exploration encompasses direct and indirect searches for new physics\, with both general-purpose and dedicated detectors. In this cont ext\, I’ll also introduce the most recent CERN experiment\, that we have just installed at the LHC\, with the goal of observing collider neutrinos for the first time\, and probing the anomalies in lepton universality. Th e broader goal is that of exploring the unmatched physics potential of the LHC to the fullest extent and into the intensity frontier we are now ente ring.Speaker: João PenedoTitle: Piecing together the Flavour puzzleAbstra ct: Despite its repeated successes\, the Standard Model is not the last wo rd in our understanding of the subatomic world. The peculiarities that set neutrinos apart from other particles hint at Neutrino Physics as the most promising gateway to Physics Beyond the Standard Model (BSM). In an era o f precision\, neutrino masses and mixing are fundamental pieces in the bro ader puzzle of Flavour. From the theoretical and phenomenological viewpo int\, one strives to find unified and testable descriptions of the known f lavour patterns which address fundamental problems in Particle Physics -- e.g. the smallness and nature of neutrino masses\, the nature of dark matt er\, the sources of matter-antimatter asymmetry and its absence in strong interactions. Such new Physics may justify tantalising anomalies in the da ta. The unprecedented sensitivities of upcoming experiments (e.g. DUNE\, B elle and SHiP) will allow us to scrutinise these BSM scenarios and persist ent deviations within the next decade.Speaker: Andreas TrautnerTitle: The Standard Model flavor puzzle and perspectives of a resolutionAbstract: Wit h decades worth of data from high precision flavor experiments and robust confirmation at the LHC\, addressing the Standard Model flavor puzzle is m ore pressing than ever. I will briefly\, pedagogically introduce the puzzl e then discuss my way to approach its resolution. This involves new mathem atical techniques\, for example\, to understand the violation of matter-an timatter symmetry\, as well as new model building extensions (including mu lti-Higgs models) to scrutinize experimental anomalies and the elementary structure of quarks\, charged leptons and neutrinos. Most importantly\, th e dynamics of the flavor structure needs to be understood in order to redu ce the number of necessary input parameters. This gives way to testable pr edictions not only at the LHC and future colliders but potentially also in the cosmological background radiation and high energy cosmic rays. Since all of this could be embedded in UV complete frameworks such as string the ory\, a correct model should reveal groundbreaking connections also to oth er important puzzles of modern particle physics such as the origin of neut rino masses\, dark matter\, or the unification of gauge interactions. LAST-MODIFIED:20221223T120106Z LOCATION:QA1.1\, south tower URL:http://df.vps.tecnico.ulisboa.pt/eventos/particle-physics-seminars/ X-ALT-DESC;FMTTYPE=text/html:Speaker: Lil iana Apolinário
Title: Unveiling the time structure of QCD jets
Abstract: H eavy-ion collisions are a unique laboratory to recreate the high energy an d density conditions prevalent during the primordial moments of our Univer se: the Quark-Gluon Plasma (QGP). This new state of matter is made of the elementary building blocks (quarks and gluons) of Quantum Chromodynamics ( QCD)\, a key ingredient of the Particle Physics Standard Model. Unveiling the characteristics of the QGP allows us to ascertain the QCD'\;s fund amental properties. This goal can be achieved in hadronic collisions throu gh jets: spray of particles that result from the fragmentation of high-ene rgy quarks and gluons produced concurrently with the collision. The fact t hat jets in proton-proton collisions are well understood has allowed us to successfully use them to extract the QGP'\;s time-averaged properties . However\, jets are evolving multi-scale objects that witness the entire space-time evolution of the system\, making them unique tools for analysin g the strong time dependence of the QGP properties. In this talk\, I will present the most recent breakthroughs that unlocked time-differential meth ods for a full time-scan of the QGP at current colliders'\; energies.< /p>
Speaker: Nuno Leonardo
Title: The LHC at the i ntensity frontier
Abstract: The LHC is our most powerful tool to probe nature at the smallest scales and most fu ndamental level. The strategy is to accumulate large datasets at high ener gies to search for tiny signals. One such signal was revealed a decade ago \, and resulted in the experimental confirmation of the last standard mode l particle. While no new particles beyond the standard model have been est ablished so far\, there is tantalising evidence of their presence in the d ata. Namely\, a persistent and significant pattern of deviations from the theory predictions has been revealed\, the so-called flavour anomalies. I ’ll present the exploration of rare signals around the flavour sector th at we’ll continue to pursue at the LHC and beyond. Such exploration enco mpasses direct and indirect searches for new physics\, with both general-p urpose and dedicated detectors. In this context\, I’ll also introduce th e most recent CERN experiment\, that we have just installed at the LHC\, w ith the goal of observing collider neutrinos for the first time\, and prob ing the anomalies in lepton universality. The broader goal is that of expl oring the unmatched physics potential of the LHC to the fullest extent and into the intensity frontier we are now entering.
Speaker: João Penedo
Title: Piecing together the Flavour puzzle
Abstract: Despite its repeated successes\, the Standard Model is not the last word in our understanding of the subato mic world. The peculiarities that set neutrinos apart from other particles hint at Neutrino Physics as the most promising gateway to Physics Beyond the Standard Model (BSM). In an era of precision\, neutrino masses and mix ing are fundamental pieces in the broader puzzle of Flavour. From the th eoretical and phenomenological viewpoint\, one strives to find unified and testable descriptions of the known flavour patterns which address fundame ntal problems in Particle Physics -- e.g. the smallness and nature of neut rino masses\, the nature of dark matter\, the sources of matter-antimatter asymmetry and its absence in strong interactions. Such new Physics may ju stify tantalising anomalies in the data. The unprecedented sensitivities o f upcoming experiments (e.g. DUNE\, Belle and SHiP) will allow us to scrut inise these BSM scenarios and persistent deviations within the next decade .
Speaker: b> Andreas Trautner
Title: The Standar d Model flavor puzzle and perspectives of a resolution
Abstract: With decades worth of data from high precision flavor experiments and robust confirmation at the LHC\, addressing the Sta ndard Model flavor puzzle is more pressing than ever. I will briefly\, ped agogically introduce the puzzle then discuss my way to approach its resolu tion. This involves new mathematical techniques\, for example\, to underst and the violation of matter-antimatter symmetry\, as well as new model bui lding extensions (including multi-Higgs models) to scrutinize experimental anomalies and the elementary structure of quarks\, charged leptons and ne utrinos. Most importantly\, the dynamics of the flavor structure needs to be understood in order to reduce the number of necessary input parameters. This gives way to testable predictions not only at the LHC and future col liders but potentially also in the cosmological background radiation and h igh energy cosmic rays. Since all of this could be embedded in UV complete frameworks such as string theory\, a correct model should reveal groundbr eaking connections also to other important puzzles of modern particle phys ics such as the origin of neutrino masses\, dark matter\, or the unificati on of gauge interactions.
END:VEVENT BEGIN:VEVENT SUMMARY:A novel magnetoresistive tactile soft-sensor\, inspired by biologi cal cilia DTSTART:20230127T100000Z DTEND:20230127T120000Z DTSTAMP:20240329T082742Z UID:aa070e65-2d28-427a-93bb-c42931d140fa SEQUENCE:1 CREATED:20230126T164506Z DESCRIPTION: Resumo: A sensação táctil é fulcral para a precisão da m otricidade humana\, e a implementação deste tipo de sensibilidade em rob ôs através do desenvolvimento de sensores tácteis é de elevada import ância para que estas máquinas tenham sensações tácteis como as nossas . Os sensores de magnetoresistência por efeito de túnel (TMR) são bons candidatos a transdutores para este tipo de dispositivos\, devido à sua e levada sensibilidade e potencial de miniaturização. Com o objectivo de p roduzir um sensor TMR altamente sensível que simultaneamente permita a de teção de campo magnético em várias direções\, a otimização de jun ções TMR de alumina sem necessidade de recozimento térmico foi realizad a\, atingindo um rácio de TMR de 35%. Um die monolítico com sensibilidad e 2D numa configuração em ponte de Wheatstone foi concebido e fabricado\ , tirando partido da dispensa de recozimento das junções TMR desenvolvid as. Adicionalmente\, de modo a modularizar o sensor e corrigir algumas das suas não-idealidades\, uma interface electrónica analógica foi desenvo lvida\, com a capacidade de ser facilmente integrada em plataformas robót icas. Foi concebido um sensor táctil inspirado na estrutura ciliar encont rada em certos seres biológicos\, que consiste numa protuberância cilín drica alongada fixa à superfície do sensor TMR 2D. Uma relação empíri ca foi encontrada para a resposta do sinal 2D em função da defleção e rotação do cílio. Diferentes configurações do sensor ciliar foram tes tadas relativamente à sua capacidade de detetar e resolver topografia em superfícies\, sendo capaz de detetar estruturas com até 20 µm de altura . A implementação de um dispositivo com capacidade para medir a textura de superfícies poderá permitir a utilização de uma nova métrica da qu alidade destes produtos\, tanto em sistemas de apanha automática como em sistemas de controlo de qualidade na cadeia de abastecimento. Maçãs e mo rangos que apresentavam duas classes de qualidade (maduro ou podre) foram testados. A precisão da classificação\, avaliada através de validaçã o cruzada com 1 fruto\, foi de 96% quando foram testadas maçãs classific adas com um classificador Bayes Gaussiano Ingénuo e 83% quando foram test adas maçãs classificadas com um algoritmo de Floresta Aleatória. Este d esempenho está em linha com aquele que é observado noutros sistemas tác teis ou baseados em análise de imagem\, demonstrando o potencial deste se nsor para o controlo de qualidade na agricultura. LAST-MODIFIED:20230126T164506Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/a-novel-magnetoresistive-tact ile-soft-sensor-inspired-by-biological-cilia/ X-ALT-DESC;FMTTYPE=text/html:Resumo:
A sensação táctil é fulcral para a precisão da mo
tricidade humana\, e a implementação deste tipo de sensibilidade em rob
ôs através do desenvolvimento de sensores tácteis é de elevada import
ância para que estas máquinas tenham sensações tácteis como as nossas
. Os sensores de magnetoresistência por efeito de túnel (TMR) são bons
candidatos a transdutores para este tipo de dispositivos\, devido à sua e
levada sensibilidade e potencial de miniaturização.
Com o obje
ctivo de produzir um sensor TMR altamente sensível que simultaneamente pe
rmita a deteção de campo magnético em várias direções\, a otimizaç
ão de junções TMR de alumina sem necessidade de recozimento térmico fo
i realizada\, atingindo um rácio de TMR de 35%. Um die monolítico com se
nsibilidade 2D numa configuração em ponte de Wheatstone foi concebido e
fabricado\, tirando partido da dispensa de recozimento das junções TMR d
esenvolvidas. Adicionalmente\, de modo a modularizar o sensor e corrigir a
lgumas das suas não-idealidades\, uma interface electrónica analógica f
oi desenvolvida\, com a capacidade de ser facilmente integrada em platafor
mas robóticas.
Foi concebido um sensor táctil inspirado na est
rutura ciliar encontrada em certos seres biológicos\, que consiste numa p
rotuberância cilíndrica alongada fixa à superfície do sensor TMR 2D. U
ma relação empírica foi encontrada para a resposta do sinal 2D em funç
ão da defleção e rotação do cílio. Diferentes configurações do sen
sor ciliar foram testadas relativamente à sua capacidade de detetar e res
olver topografia em superfícies\, sendo capaz de detetar estruturas com a
té 20 µm de altura.
A implementação de um dispositivo com ca
pacidade para medir a textura de superfícies poderá permitir a utilizaç
ão de uma nova métrica da qualidade destes produtos\, tanto em sistemas
de apanha automática como em sistemas de controlo de qualidade na cadeia
de abastecimento.
Maçãs e morangos que apresentavam duas class
es de qualidade (maduro ou podre) foram testados. A precisão da classific
ação\, avaliada através de validação cruzada com 1 fruto\, foi de 96%
quando foram testadas maçãs classificadas com um classificador Bayes Ga
ussiano Ingénuo e 83% quando foram testadas maçãs classificadas com um
algoritmo de Floresta Aleatória. Este desempenho está em linha com aquel
e que é observado noutros sistemas tácteis ou baseados em análise de im
agem\, demonstrando o potencial deste sensor para o controlo de qualidade
na agricultura.
Abstract:
We show that virtual particles\, despite being un
observable\, can be described by quantum operators which can be interprete
d under certain conditions as valid quantum states with interesting connec
tions to quantum information.
For virtual fermions\, we prove th
at such states can be regarded as 2-qubit thermal states and study their e
ntanglement. For spin-1 virtual bosons and virtual pairs of fermions\, we
find them to be associated to 4-qubit operators containing all the details
of the interactions.
Finally\, we study how renormalization aff
ects these results. These findings represent new connections between quant
um field theory\, quantum information and quantum thermodynamics.
Speaker: Rub en Conceição
Title: Exploring the ex treme energy Universe
Abstract: Ultra- high-energy cosmic rays (UHECRs) and very high-energy gamma rays are the h ighest-energy known particles and radiation\, respectively. Their study al lows us to probe some of the most extreme phenomena in our Universe and to investigate its fundamental physics properties. The Pierre Auger Observat ory\, with its upgrade\, AugerPrime\, and the future Southern Wide-field G amma-ray Observatory\, are two of the most ambitious astroparticle physics facilities in the world. In this talk\, I will briefly discuss the techno logical challenges and physics opportunities connected with the study of t hese physics objects\, which defy our understanding about acceleration mec hanisms and particle interactions.
Speaker: Catarina Cosme
Title: Glimpses of a physicist journey to the dark side of th e Universe
Abstract: In this talk\, I will introduce myself\, give an overview of my academic path\, and briefly discuss the main lines of investigation that I have pursued so far. I wil l pay special attention to the dynamics and phenomenology of non-thermal D ark Matter candidates\, in both standard and non-standard cosmologies. Fin ally\, I will give a taste of future projects I want to follow.
Speaker: Luiz Vale Silva
Title: Opportunities in a high- statistics era for flavor physics: novel predictions of the Standard Model and New Physics probes
Abstract: Flavo r physics plays a central role in particle physics: for instance\, it led to the discovery of Charge-Parity (CP) violation. I discuss briefly the cu rrent and future status of the extraction of the CKM matrix elements in th e Standard Model (SM). I also comment on the role charm physics can play i n testing the Kobayashi-Maskawa mechanism\, responsible for generating CP violation in the quark sector of the SM. Finally\, I discuss bounds on dif ferent categories of generic New Physics contributions.
Speaker: Cristóvão Vilel a
Title: Neutrino experiments at the i ntensity and energy frontiers
Abstract: Neutrinos are some of the least well understood particles in the Standar d Model (SM) and play a central role in major open questions in Physics: H ow did matter come to dominate over antimatter in the history of the Unive rse? Are there symmetries underlying the flavour structure of the SM? Why are neutrino masses so small? In this talk I will briefly describe two neu trino experiments which will help elucidate these puzzles: DUNE\, which is set to discover or rule out matter-antimatter asymmetry in neutrino oscil lations\; and SND@LHC\, which will measure for the first time interactions of neutrinos of all three flavours produced at CERN'\;s Large Hadron Collider.
END:VEVENT BEGIN:VEVENT SUMMARY:8º Workshop do MEFT DTSTART:20230208T093000Z DTEND:20230208T180000Z DTSTAMP:20240329T082742Z UID:05800b7b-4e7b-47b8-93e5-0538f2542724 SEQUENCE:6 CREATED:20230202T113557Z DESCRIPTION:Convidamos toda a comunidade do Instituto Superior Técnico a participar na 8ª edição do Workshop dos alunos do mestrado de Engenhari a Física Tecnológica. O objetivo do encontro é permitir a divulgação dos projetos que cada aluno irá realizar no âmbito da sua Dissertação de Mestrado.O encontro vai decorrer nos dias 8 e 9 de fevereiro de 2023\, das 9h30 às 18h00h\, no Anfiteatro Abreu Faro. O programa do workshop est á disponível neste link.Este workshop é parte integrante da disciplina "\;Projeto Integrador de 2º Ciclo em Engenharia Física Tecnológica& quot\; do curso de mestrado de engenharia Física Tecnológica.Comité Cie ntífico:Ílidio LopesGonçalo FigueiraPatricia GonçalvesPedro RibeiroOrg anização:Francisco PaisDiogo GonçalvesDuarte FeiteiraDavid LopesEufémi o MarquesMaria GóisPaulo FigueiredoMiguel GonçalvesJoão Patrício LAST-MODIFIED:20230202T124200Z LOCATION:Anfiteatro Abreu Faro URL:http://df.vps.tecnico.ulisboa.pt/eventos/8meftworkshop/ X-ALT-DESC;FMTTYPE=text/html:Convidamos toda a c omunidade do Instituto Superior Técnico a participar na 8ª edição do W orkshop dos alunos do mestrado de Engenharia Física Tecnológica. O objet ivo do encontro é permitir a divulgação dos projetos que cada aluno ir á realizar no âmbito da sua Dissertação de Mestrado.
O encontro vai decorrer nos dias 8 e 9 de fevereiro de 2023\,
das 9h30 às 18h00h\, no Anfiteatro Abreu Faro. O programa do workshop est
á disponível neste link.
Este workshop é parte integrante da d
isciplina "\;Projeto Integrador de 2º Ciclo em Engenharia Física Tec
nológica"\; do curso de mestrado de engenharia Física Tecnológica.<
br/>
Comité Científico:
Organização:
Abstract:
Photon-photon collisions may provide the conditions to study particle pr
oduction with masses at the electroweak scale. By tagging the leading prot
on from the hard interaction\, the Precision Proton Spectrometer (PPS) pro
vides an increased sensitivity to select exclusive processes and probe the
standard model (SM).
PPS is a detector system at approximately
210 m from the interaction point around the CMS detector\, and it is desig
ned to perform measurements of e.g. the quartic gauge couplings and search
for rare exclusive processes. Since 2016\, PPS has been taking data in no
rmal high-luminosity proton-proton LHC collisions.
A search for
exclusive processes using data collected by the CMS experiment is performe
d and the results obtained are presented.
ABSTRACT:
The study of vacuum critical collapse has acquired a
n aura of unapproachability in its 30 years of existence. It is often thou
ght that only highly sophisticated numerical methods together with immense
supercomputer clusters will suffice for treating this problem. My recentl
y defended PhD thesis questions this folk lore by using only open-source c
ode running on single machines to discover universal echoing in near-criti
cal axisymmetric vacuum spacetimes. In this talk I will discuss my work fr
om the software-development perspective.
I will describe the app
roaches\, tools\, and techniques I used to make the most of the limited de
velopment manpower and computing resources available to me. Some of these\
, such as writing assembly code by hand in order to access vector capabili
ties of modern CPUs\, come from my multimedia-software background and are
not commonly encountered in physics codes.
ABSTRACT: p>
There is good reason to think that gravitation
al wave physics\, and particularly single black hole perturbation theory\,
is at a turning point. In this talk\, I will review some of the challenge
s currently facing our understanding of single perturbed black holes.
The setting of this review will be gravitational waves from the merg
er of stellar mass binary black holes (BBHs)\, and related conceptual tens
ions. I will pay particular attention to the relevance of Kerr “quasi-no
rmal modes” (QNMs) to BBH merger\, and I will discuss how our burgeoning
understanding of QNM orthogonality points the way to new directions of re
search. As an example\, I will present a proof-of-concept for a purely spe
ctral method of solving Teukoslky’s radial equation.
Resumo
Ao atravessarem o sistema solar os raios cósmic
os deparam-se com um fluxo de plasma magnetizado altamente condutor que em
ana do Sol\, conhecido como Vento Solar\, que transporta o turbulento camp
o magnético solar e com o qual estes interagem. Devido à atividade solar
\, a heliosfera está sujeita a variações de curta e longa duração que
se refletem no fluxo de raios cósmicos na forma de variabilidade tempora
l\, especialmente a baixas energias (até cerca de 50 GeV)\, na proximidad
e da Terra.
Esta variabilidade da intensidade de raios cósmicos
na heliosfera é conhecida como Modulação Solar dos Raios Cósmicos Gal
ácticos. O Espectrómetro Magnético de Partículas Alfa (AMS-02) é um d
etetor de raios cósmicos de alta precisão instalado na Estação Espacia
l Internacional (ISS) que observa continuamente o fluxo de raios cósmicos
e as suas variações no tempo\, posicionando-se como uma plataforma úni
ca para estudar Modulação Solar. Nesta tese caracterizou-se de forma int
rodutória os raios cósmicos e relevou-se AMS enquanto o detetor usado pa
ra os observar e estudar.
Estudou-se a estimativa do fluxo de ra
ios cósmicos em grande detalhe enquanto se analisou o desempenho dos dife
rentes sub-detetores envolvidos. Descreveu-se o processo através do qual
se utilizou a grande precisão de AMS e dos seus sub-detetores para identi
ficar as astro-partículas que esta deteta e como foi estimado o fluxo res
olvido em tempo com uma resolução de 27 dias (conhecida como rotação s
olar Bartel). Foi introduzido o processo físico da Modulação Solar e ap
resentou-se uma revisão da equação de transporte de Parker e as suas li
gações ao campo magnético solar através dos parâmetros de propagaçã
o.
Utilizando técnicas modernas de análise de frequências\, c
aracterizou-se o fluxo de protões resolvido no tempo\, quer no domínio d
o tempo quer das frequências\, e correlacionouse o mesmo com as diferente
s periodicidades temporais presentes no Ciclo de Atividade Solar. 2 Usando
um modelo do transporte de raios cósmicos na heliosfera\, em combinaçã
o com uma grande coleção de dados experimentais\, mostrou-se evidência
de um atraso temporal de 8 meses entre as observações do ciclo de ativid
ade solar e o fluxo de raios cósmicos medido no espaço. Este resultado p
ermite prever o fluxo de raios cósmicos na Terra através da observação
da atividade solar.
Abstract:
The
European Strategy for Particle Physics update remarks on the importance of
the detectors'\; R&\;D in preparation for the Future Circular Coll
ider (FCC). In scintillator-based calorimeter systems\, a high energy reso
lution is needed for an FCC electron-positron collider\, while a hadron co
llider option requires high radiation hardness.
The study of the
degradation history of current operating detectors in actual experimental
conditions\, such as those of the ATLAS hadronic calorimeter TileCal\, is
fundamental in this context. In this work\, a study of the ageing of the
TileCal hadronic calorimeter due to radiation exposure is presented.
<
br/>In addition\, a TileCal-like design will be proposed for an FCC electr
on-positron collider detector. Initial simulation studies on the design of
this calorimeter\, considering decisive factors such as the geometry\, th
e sampling fraction and the energy resolution\, were performed and will al
so be presented.
Abstract: p>
In this thesis\, we consider the implementati
on of a quantum computer in systems of BoseEinstein condensates\, quantum
vortices and impurities as a roadmap to the investigation of the fundament
al physics of these systems. We consider questions of structure\, scalabil
ity\, dynamical stability\, robustness against decoherence/perturbations\,
amenability to external control and availability of quantum resources\, w
hich are necessary elements to encode and perform error-tolerant quantum i
nformation processing. BECs with vortices are a good platform to explore t
hese questions\, since it is well known that vortices in this superfluid a
re dynamically stable\, topologically robust\, stationary configurations t
hat can be created in large numbers to form Abrikosov lattices.
Their robustness\, structure and scalability suggests the realization of q
ubits by making impurities occupy the vortex core. Thus\, we began by char
acterizing these bound states to establish a good basis on which to encode
a qubit. The next step was to characterize the excitations of the vortex-
BEC. Motivated by questions of robustness\, we introduced a measure that c
haracterizes these excitations with respect to their interactions with any
impurity.
We found that some characteristic excitation modes of
this system have an exceptional capacity to interact with impurities\, wh
ich lead us to suggest a novel mechanism of quantum-level control of impur
ities. With this work\, we have also established that the low-energy excit
ations of the vortex-BEC have an anomalous dispersion. We then studied the
interactions between the two parts of the system\, and found that the res
ulting collective excitations obey a deformed quantum statistics\, known a
s para-Bose statistics.
We characterized geometrically the singl
e-body state of these excitations\, known to be non-classical\, and found
a non-trivial geometric phase. In turn\, the many-body states indicate tha
t the excitations are in a condensed state. We attempt to characterize thi
s condensate and discuss its implications towards this system as a quantum
platform.
ABSTRACT:
The knowledge of compact stellar remnants\, neutron stars and black holes\, has greatly expanded in recent years. Many of the dogmas of the past were refuted and we face a new era in which the pieces of the puzzle are difficult to fit\, but on the other hand many opportunit ies to contribute appear. I shall discuss in this seminar some of the latt er\, including the masses and mass distribution of both objects\, their bi rth in stellar collapses and other events\, and related topics.
END:VEVENT BEGIN:VEVENT SUMMARY:Confinement in QED DTSTART:20230301T143000Z DTEND:20230301T160000Z DTSTAMP:20240329T082742Z UID:800272ec-58f4-4405-8428-4eeac75e5ffc SEQUENCE:2 CREATED:20230222T152238Z DESCRIPTION:It is believed that in QCD its fundamental constituints are co nfined\, i.e. that the Hilbertspace of the physics states does not include single quark or gluon states. How thisproperties translates into two poin t correlation functions is not clear. Certainly\,positivity violation is a n indication of confinement. Do we have other theories whereconfinement ta kes place? Indeed\, this happens for the compact formulation on latticeof QED that has two phases: a confined and a non-confined phase. Then\, how d o theparticle propagators look like in each phase? What about positivity v iolation? In orderto help answering these questions\, we revist the photon propagator for the puregauge theory. In the confined case we show that it has an associated linearly growingpotential\, it has a mass gap\, that is related to the presence of monopoles\, and itsspectral function is not po sitive defined. In the non-confining phase\, our simulationssuggest that a free field theory is recovered in the thermodynamic limit. LAST-MODIFIED:20230222T154707Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/orlando-oliveira/ X-ALT-DESC;FMTTYPE=text/html:It is believed that
in QCD its fundamental constituints are confined\, i.e. that the Hilberts
pace of the physics states does not include single quark or gluon states.
How thisproperties translates into two point correlation functions is not
clear.
Certainly\,positivity violation is an indication of confi
nement. Do we have other theories whereconfinement takes place? Indeed\, t
his happens for the compact formulation on latticeof QED that has two phas
es: a confined and a non-confined phase.
Then\, how do thepartic
le propagators look like in each phase? What about positivity violation? I
n orderto help answering these questions\, we revist the photon propagator
for the puregauge theory.
In the confined case we show that it
has an associated linearly growingpotential\, it has a mass gap\, that is
related to the presence of monopoles\, and itsspectral function is not pos
itive defined. In the non-confining phase\, our simulationssuggest that a
free field theory is recovered in the thermodynamic limit.
Abstract: In vestigations into the topology of band structures in solid state physics h as been one of the most important conceptual and experimental enterprises in the physics of this century. In this talk I give a broad introduction t o the state of the field. Then I shall focus on my own work on extending e xisting ideas into the realm of band structures of magnetic excitations an d the connections with interesting open directions in quantum magnetism. I will say something about bulk probes of Dirac and Weyl magnons\, surface probes of magnetism\, the zoo of topological magnon states and the role of magnon interactions in shaping\, destroying and creating nontrivial topol ogy. I shall also connect these findings to transport and spectroscopic ex periments on a variety of magnetic materials.
END:VEVENT BEGIN:VEVENT SUMMARY:A next-generation gamma-ray observatory powered by machine learnin g techniques DTSTART:20230302T110000Z DTEND:20230302T130000Z DTSTAMP:20240329T082742Z UID:3941d0fc-6196-4ba2-9098-23abf9d7589c SEQUENCE:5 CREATED:20230301T085456Z DESCRIPTION:Abstract:The Southern Wide-field Gamma-ray Observatory (SWGO) is the next-generation ground-based gamma-ray observatory to survey the So uthern hemisphere sky. The experiment\, currently in an R&\;D phase\, i s expected to have a large array of a few square kilometers composed of wa ter Cherenkov detectors (WCDs) placed at a high altitude (4.4 km a.s.l. or higher) in South America. Such an ambitious project requires the design o f a high-performance and cost-effective WCD to cope with the observatory n eeds\, particularly the capability to identify shower muons\, which is ess ential to ensure excellent gamma/hadron discrimination.In this work\, it i s shown that efficient muon tagging (and counting) can be achieved using w ater Cherenkov detectors with a reduced water volume and multiple PMTs\, p rovided that the PMT signal spatial and time patterns are interpreted by a n analysis based on Machine Learning (ML).The proposed WCDs would highly b oost the physics capabilities of SWGO\, enabling it to cover\, with a wide field of view\, a wide energy range\, from low energies ($\\sim$ 100 GeV) up to the PeV region. LAST-MODIFIED:20230301T085624Z LOCATION:Online (Password: 267692) URL:http://df.vps.tecnico.ulisboa.pt/eventos/a-next-generation-gamma-ray-o bservatory-powered-by-machine-learning-techniques/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
The Southern Wide-field Gamma-ray Observatory (SWGO) is the next-generat
ion ground-based gamma-ray observatory to survey the Southern hemisphere s
ky. The experiment\, currently in an R&\;D phase\, is expected to have
a large array of a few square kilometers composed of water Cherenkov detec
tors (WCDs) placed at a high altitude (4.4 km a.s.l. or higher) in South A
merica.
Such an ambitious project requires the design of a high-
performance and cost-effective WCD to cope with the observatory needs\, pa
rticularly the capability to identify shower muons\, which is essential to
ensure excellent gamma/hadron discrimination.
In this work\, it
is shown that efficient muon tagging (and counting) can be achieved using
water Cherenkov detectors with a reduced water volume and multiple PMTs\,
provided that the PMT signal spatial and time patterns are interpreted by
an analysis based on Machine Learning (ML).
The proposed WCDs would hi
ghly boost the physics capabilities of SWGO\, enabling it to cover\, with
a wide field of view\, a wide energy range\, from low energies ($\\sim$ 10
0 GeV) up to the PeV region.
ABSTRACT:
Though General Relativity has been successfully test
ed so far\, concepts such as dark energy and string theory suggest the nee
d of modifying it. Scalar-tensor theory is one of the most popular alterna
tives discussed. We produce studies of stellar core collapse in spherical
symmetry in which we systematically explore the parameter space that chara
cterizes the progenitor stars\, the equation of state and the scalar-tenso
r theory of the core collapse events.
We identify a remarkably s
imple and straightforward classification scheme of the resulting collapse
events. For any given set of parameters\, the collapse leads to one of thr
ee end states\, a weakly scalarized neutron star\, a strongly scalarized n
eutron star or a black hole\, possibly formed in multiple stages. The latt
er two end states can lead to strong gravitational-wave signals that may b
e detectable in present continuous-wave searches with ground-based detecto
rs.
The dispersive nature of the propagation of waves in the mas
sive scalar field means the gravitational wave signals are long lived and
many such signals can overlap to form a stochastic background. Using diffe
rent models for the population of supernova events in the nearby universe\
, we compute predictions for the energy-density in the stochastic scalar-p
olarized gravitational wave background from core-collapse events in massiv
e scalar-tensor gravity for theory parameters that facilitate strong scala
rization.
Resumo:
< p data-block-key="ecd4c">Smart colloidal nanocrystals\, namely colloidal c halcogenides and halide perovskites\, have recently received much attentio n due to their extraordinary properties\, such as tunable\, very sharp emi ssion\, faster carrier recombination\, low-threshold lasing properties\, a nd higher stability in ambient atmosphere.ABSTRACT:
Accurate signal models are essential in the anal
ysis of gravitational wave events\, from parameter estimation to astrophys
ical interpretation and tests of general relativity. As detectors get incr
easingly advanced it becomes ever more crucial to develop precision models
of signals from a wide range of physical systems\, including black-holebi
naries where the spins are not aligned with the orbital angular momentum
— precessing binaries.
Evidence for a population of such syste
ms has already been seen during the third observing run of the LVK and thi
s is expected to become stronger in the upcoming run. I will discuss recen
t developments that have resulted in the first complete inspiral-mergerrin
gdown model of the gravitational wave signal from a precessing binary wher
e the precession effects have been tuned to numerical relativity through m
erger and ringdown as well as a more complete understanding of the phenome
nology of such systems.
Particle accelerato
rs have been engines of discovery in our understanding of the Universe and
have applications in many areas of modern life from medicine to security.
The most powerful ones are 10’s of kilometers in length\, determined by
the strength of the accelerating electric field. It has been four decades
since the concept of using a relativistic plasma wake for charged particl
e acceleration was first proposed.
In relativistic plasma wakes
the accelerating electric field can be orders of magnitude greater than in
a conventional accelerator with the potential to reduce the size of the a
ccelerating structure. The driver for producing such wakes can be in inten
se laser pulse or a high current charged-particle beam.
During t
his time ingenious solutions for generating the ultra-high electric field
over meter-scale distances\, and generating and accelerating high quality
electron and positron beams using such wakes have been realized. In this t
alk I will give a personal perspective on the progress of the field of pla
sma-based acceleration driven by ultrashort electron bunches and where it
is headed
We address the effe ct of disorder on the topological surface (“drumhead”) states of a Wey l nodal loop semimetal. Two types of disorder are considered:
Anderson disorder breaks chiral symmetry\, so\, a topol
ogical index is not defined. Weak disorder produces the algebraic decay
of the E=0 surface states into the bulk\, and a broadening of the low ener
gy density of surface states by degeneracy lifting. This behavior persists
up to the bulk semimetal/metal transition at the critical disorder\, Wc \
, above which all surface states hybridize with bulk states and become e
xtended.
Weak chiral disorder induces a diffusive metal at zero
energy and\, surprisingly\, enhances the number of topological surface st
ates as confirmed by the winding number and the low energy DOS of the open
system. The topological surface states are exponentially localized into t
he bulk\, and exhibit a multifractal structure on the surface.
T
his is a novel topological metal hosting topological multifractal surface
states. The number of surface states decreases either algebraically with d
isorder\, or exponentially if the latter only affects intracell hoppin
gs.
Resumo:
Dark matter is one of the biggest mysteries in p hysics. Could it be made of new light particles that form self-gravitating structures called boson stars? In this talk\, I will explore what happens when a black hole collides with a boson star. Using numerical simulations in general relativity\, I will show how the black hole swallows most of t he boson star material and emits gravitational waves. I will also discuss the formation of a “gravitational atom” as a remnant of the collision. This talk will shed light on the nature and fate of these exotic objects in our universe.
END:VEVENT BEGIN:VEVENT SUMMARY:Effective field theory of black hole perturbations with timelike s calar profile DTSTART:20230316T143000Z DTEND:20230316T160000Z DTSTAMP:20240329T082742Z UID:326bf911-7e53-4752-afcd-f949f04bc391 SEQUENCE:1 CREATED:20230310T142449Z DESCRIPTION:Abstract: Many dark energy (DE) models are based on a scalar f ield with timelike gradient. If one hopes to learn something about scalar field DE from astrophysical black holes (BHs) then one needs to consider B H solutions with timelike scalar profiles. In this talk we begin with a re view of the systematic construction of the effective field theory (EFT) de scribing perturbations around Minkowski and cosmological backgrounds with timelike scalar profiles. We then extend the EFT to arbitrary backgrounds. Finally\, as an application of the general EFT\, we study odd-parity pert urbations around a spherically symmetric\, static black hole background wi th a timelike scalar field responsible for DE. LAST-MODIFIED:20230310T142449Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/effective-field-theory-of-bla ck-hole-perturbations-with-timelike-scalar-profile/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
Many dark energy (DE) models are based on a scalar field with timelike
gradient. If one hopes to learn something about scalar field DE from astro
physical black holes (BHs) then one needs to consider BH solutions with ti
melike scalar profiles.
In this talk we begin with a review of t
he systematic construction of the effective field theory (EFT) describing
perturbations around Minkowski and cosmological backgrounds with timelike
scalar profiles.
We then extend the EFT to arbitrary backgrounds
. Finally\, as an application of the general EFT\, we study odd-parity per
turbations around a spherically symmetric\, static black hole background w
ith a timelike scalar field responsible for DE.
Describing interac
ting quantum systems in the presence of dissipation is a daunting task. On
e very fruitful approach to this problem\, developed for unitary dynamics\
, is to represent the Hamiltonian of a generic system by a large random ma
trix. This approach eventually led to the development of the field of quan
tum chaos.
Here\, I will give an overview of the recent applicat
ion of (non-Hermitian) random matrix theory to open quantum systems\, wher
e dissipation and decoherence coexist with unitary dynamics. I will discus
s the spectral features\, relaxation timescales\, and steady states of thr
ee representative examples of increasing physical relevance: fully random
Lindbladians and quantum maps\, random open free fermions\, and dissipativ
e stronglyinteracting SYK models.
Then\, I will argue that compl
ex spacing ratios are a powerful signature of dissipative quantum chaos\,
illustrating it with the case of boundary-driven spin-chain Lindbladians.
Title: From III-Nitride nanowires to the fabrication of nano-structured piezoelectric transducers
Speaker: Dr. Noelle Gog neau
Abstract: The number of “In ternet of Things” (IoTs) is constantly on a rise both in our daily life and in high-tech applications. Today\, the question of their energetic aut onomy is a key worldwide challenge. The recent miniaturization of electron ic micro-devices\, thus resulting in the reduction of their energy consump tion to mW and even µW\, combined with the progress in micro-nano-fabrica tion\, have opened new perspectives to develop autonomous power systems ba sed on the renewable energy harvesting. Among renewable energies\, the mec hanical deformations and vibrations\, harvested using piezoelectric materi als\, present the advantages to be ubiquitous and permanently available. p>
A new class of transducers has appeared these l ast years\, integrating nanomaterials such as 1D-nanostructures. Thanks to their large surface-to-volume\, high crystalline quality and nanoscale di mensions\, semiconductor nanowires (NWs) present unique advantages to sign ificantly enhance the piezo-device performances. The attention has turned to III-Nitride NWs thanks to their high-piezoelectric coefficients and the ir strong piezo-generation response [1\,2].
H ere\, we present the piezo-generation with Ga(In)N NWs going from the NW s ynthesis to the fabrication and testing of transducers. Our approach is ba sed on systematic multiscale analyses. Starting from the characterization of the piezoelectric properties of unique NWs and the investigation of the piezo-mechanisms in play [3-5]\, we then demonstrate the high piezoelectr ic conversion properties of NWs on a device level [6-7].
References
[1] N. Gogneau et al. Phys. Status Solidi RRL 8\, 414 (2014).
[2] N. Jegenyes\, N. Gogneau et al. Nanomaterials 8 \, 367 (2018).
[3] N. Jamond\, N. Gogneau et al. Nanoscale 9\, 4610 (2017).
[4] N. Gogneau\, M. Tchernycheva et al. Semicond. Sci. Technol. 31\, 103002 (2016).
[5] N. Gogneau\, P. C hrétien\, T. Sodhi et al. Nanoscale\, 14\, 4965 (2022).
[6] N. Jamond\, N. Gogneau et al. Nanotechnol ogy 27\, 325403 (2016).
[7] L. Lu\ , N. Gogneau\, M. Tchernycheva et al Conference IEEE-NANO (2018). p> END:VEVENT BEGIN:VEVENT SUMMARY:Conditions for constraint preservation and gauge fixing in well po sed theories: application to gravitation DTSTART:20230323T143000Z DTEND:20230323T160000Z DTSTAMP:20240329T082742Z UID:bc836a5c-238a-4680-ad41-a751f5f7d303 SEQUENCE:1 CREATED:20230317T140924Z DESCRIPTION: ABSTRACT: We use Partial Differential Equations (PDEs) to des cribe physical systems\; in general\, these equations include evolution an d constraint equations. One method used to find solutions to these equatio ns is the free-evolution approach\, which consists in obtaining solutions of the entire system by solving only the evolution equations. Certainly\, this is valid only when the chosen initial data satisfies the constraints\ , and the constraints are preserved in the evolution. In this talk\, we wi ll establish sufficient conditions for generic first order PDEs to guarant ee the constraint preservation. For this purpose\, we will discuss the str ong hyperbolicity of the PDEs and their connection with the Kronecker deco mposition of matrix pencils. Another method for finding solutions of PDEs with constraints is through extensions\; some well-known examples are dive rgence cleaning for Electrodynamics and Z4 for Einstein equations. We will discuss how Kronecker decomposition suggests families of strongly hyperbo lic extensions. Finally\, we will discuss how this scheme can be extrapola ted to PDEs that include Gauge freedom\, providing a guide for fixing thos e freedoms in a well-posed way. We will show how these ideas apply to Eins tein equations. LAST-MODIFIED:20230317T140924Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/conditions-for-constraint-pre servation-and-gauge-fixing-in-well-posed-theories-application-to-gravitati on/ X-ALT-DESC;FMTTYPE=text/html:
ABSTRACT: < /p>
We use Partial Differential Equations (PDEs)
to describe physical systems\; in general\, these equations include evolut
ion and constraint equations. One method used to find solutions to these e
quations is the free-evolution approach\, which consists in obtaining solu
tions of the entire system by solving only the evolution equations.
<
br/>Certainly\, this is valid only when the chosen initial data satisfies
the constraints\, and the constraints are preserved in the evolution. In t
his talk\, we will establish sufficient conditions for generic first order
PDEs to guarantee the constraint preservation. For this purpose\, we will
discuss the strong hyperbolicity of the PDEs and their connection with th
e Kronecker decomposition of matrix pencils.
Another method for
finding solutions of PDEs with constraints is through extensions\; some we
ll-known examples are divergence cleaning for Electrodynamics and Z4 for E
instein equations.
We will discuss how Kronecker decomposition sugges
ts families of strongly hyperbolic extensions.
Finally\, we will
discuss how this scheme can be extrapolated to PDEs that include Gauge fr
eedom\, providing a guide for fixing those freedoms in a well-posed way. W
e will show how these ideas apply to Einstein equations.
Abstract:
The p
roperties of the Higgs boson together with the absence of new physics at t
he Large Hadron Collider allow us to speculate about consistently extendin
g the Standard Model all the way up to the Planck scale while staying in t
he perturbative regime.
In this context\, the SM Higgs non-minim
ally coupled to gravity could be responsible for the symmetry properties o
f the Universe at large scales and the generation of the primordial spectr
um of temperature fluctuations seen in the Cosmic Microwave Background (CM
B).
In this work we show how Higgs-Inflation and its scale-invari
ant extension\, known as Higgs-Dilaton inflation\, can be embedded in Eins
tein-Cartan gravity.
In particular we will discuss some phenomenologic
al features emerging from the inflationary and post-inflationary dynamics.
Abstract:
NMR relaxometry is widely applied in the study of v
ery diverse chemical systems\, such as polymers\, ionic liquids\, liquid c
rystals and magnetic fluids. The molecular motions that characterize each
system\, occurring within timescales that range from picoseconds to millis
econds\, are encoded in their relaxation dispersion profiles. Such motions
generally include rotations/reorientations\, as well as translational sel
fdiffusion\, which should\, in theory\, be the necessary and sufficient co
ntributions to explain the NMRD profiles of non-magnetic\, isotropic syste
ms. Regarding liquid crystalline phases\, order fluctuations are usually t
he most effective relaxation mechanism\, while for magnetic systems parama
gnetic relaxation often dominates the NMR relaxometry profile.
R
ecent works evidenced local order fluctuation dynamics in isotropic liquid
s\, very far from the glass transition\, either due to nano-segregation of
polar-apolar domains\, revealed by the X-ray profiles\, or as a result of
marked molecular anisometry. The present work mainly combines 1H NMR rela
xometry and diffusometry with X-ray scattering experiments in the study of
the molecular dynamics of magnetic and non-magnetic ionic liquids based o
n the [P6\,6\,6\,14] + and [C8mim]+ cations and on PEG-based magnetic sy
stems.
The data obtained from all these three experimental techn
iques evidenced the need to consider either order parameter fluctuations o
r layer undulations in the NMRD model fitting analysis of these systems\,
despite their apparent isotropic nature. This observation indicates that N
MR is sensitive both to the existence of local order\, as well as to the c
haracteristics of that order - orientational and positional. The electrica
l properties of the ionic liquids were additionally assessed via electroch
emical impedance spectroscopy\, being potentially interesting for dielectr
ic applications\, as relative permittivities of about 1000 were obtained.
The next generatio
n of lasers will access intensities above 10^23 W/cm^2. When plasmas or re
lativistic electron beams interact with these lasers\, energy loss due to
radiation emission\, or quantum effects such as electron-positron pair cre
ation become important for their dynamics.
Repeated occurrence o
f pair creation can induce a socalled “QED cascade”\, that generates a
n exponentially rising number of particles. This allows for creating exoti
c plasmas that are a mix of electrons\, ions\, positrons\, energetic photo
ns and intense background fields. Extreme laser-plasma interactions can be
explored to form optical traps\, create&\;accelerate particles and pro
duce novel radiation sources.
I will introduce a QED module coup
led with the massively particlein-cell framework OSIRIS that allows studyi
ng nonlinear plasma dynamics in the transition from the classical to the q
uantum-dominated regime of interaction and discuss the possibilities for e
lectron-positron pair creation and acceleration in nearfuture experiments.
Speaker: Prof. Mark Kushner\, The University of Michigan
Title: Plasmas for Microelectronics Fabrication: A Modeling Perspective
Abstract: The impressive advances in the capabilities of microelectronics logic and memory devices are largely due to plasma-based etching\, deposition\, cleaning\, sputter ing and passivation processes that have been translated to high volume man ufacturing (HVM). Memory device architectures require etching high aspect ratio (HAR) features of only tens of nm diameter with aspect ratios exceed ing 100. Logic devices now require removing or adding materials with atomi c layer accuracy – atom layer etching (ALE) and atomic layer deposition (ALD). These manufacturing steps can now only be provided in HVM using pla sma processes. Modeling and simulation (M&\;S) for both reactor and fea ture scale plasma processing has long served a supporting role. However\, with HAR\, ALE and HVM challenges at the forefront\, M&\;S for plasma b ased device fabrication has received renewed attention to provide (or insp ire) new equipment and process designs\, and new insights. In this talk\, the status of M&\;S for plasma processing will be surveyed. An overview and "\;quick-plasma"\; tutorial will first be provided\, followed by a description of the numerical techniques used for reactor and feature scale modeling. Using examples from the speaker’s research group\, the model-based scaling and optimization of plasma etching reactors will be di scussed (e.g.\, multi-frequency\, capacitively coupled plasmas for HAR etc hing and pulsed inductively coupled plasmas for front-end processing). The coupling of reactor-scale reactive fluxes to feature scale modeling of AL E and ALD\, and HAR of ONO (oxide-nitride-oxide) stacks for high-density m emory will be discussed\, as well the role of machine learning for process design.
*Work supported by the DOE Office of Fusion Energy Science\, National Science Fo undation\, Lam Research Inc. and Samsung Electronics Co. Ltd.
END:VEVENT BEGIN:VEVENT SUMMARY:Conformal Symmetry in the Standard Model and its Symbiosis with Gr avity DTSTART:20230330T143000Z DTEND:20230330T160000Z DTSTAMP:20240329T082742Z UID:815e1f6a-2bf7-45fa-96d2-047fceb323a3 SEQUENCE:1 CREATED:20230327T085354Z DESCRIPTION: ABSTRACT: I will discuss how (broken) conformal symmetry can be used as a guiding principle to construct viable minimalistic extensions of the Standard Model. I will highlight the central role gravity (and its incarnations) plays in these considerations\, with an emphasis on the Ein steinCartan formulation. I will show that an inflationary epoch driven by the Higgs field is automatically incorporated. Moreover\, the inflationary predictions may in principle be related to the electroweak physics\, thus creating an intricate link between the primordial and late Universe. Fina lly\, I will comment on the self-consistency of these constructions. LAST-MODIFIED:20230327T085354Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/conformal-symmetry-in-the-sta ndard-model-and-its-symbiosis-with-gravity/ X-ALT-DESC;FMTTYPE=text/html:ABSTRACT: < /p>
I will discuss how (broken) conformal symmetr y can be used as a guiding principle to construct viable minimalistic exte nsions of the Standard Model. I will highlight the central role gravity (a nd its incarnations) plays in these considerations\, with an emphasis on t he EinsteinCartan formulation. I will show that an inflationary epoch driv en by the Higgs field is automatically incorporated. Moreover\, the inflat ionary predictions may in principle be related to the electroweak physics\ , thus creating an intricate link between the primordial and late Universe . Finally\, I will comment on the self-consistency of these constructions.
END:VEVENT BEGIN:VEVENT SUMMARY:Non-linear Electrodynamics derived from the Kaluza-Klein Theory DTSTART:20230406T143000Z DTEND:20230406T160000Z DTSTAMP:20240329T082742Z UID:fb94e575-971a-4dee-9b1a-06871627882f SEQUENCE:1 CREATED:20230331T111339Z DESCRIPTION: ABSTRACT: The lagrangian of the Kaluza-Klein theory\, in its simplest five-dimensional version\, should include not only the scalar cur vature R\, but also the quadratic GaussBonnet invariant. The general lagra ngian is computed and the resulting non-linear equations which genralize M axwell'\;s system in a quite unique way are investigated. The possibil ity of the existence of static solutions is presented\, and the qualitativ e behaviour of such solutions is discussed. LAST-MODIFIED:20230331T111339Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/non-linear-electrodynamics-de rived-from-the-kaluza-klein-theory/ X-ALT-DESC;FMTTYPE=text/html:ABSTRACT: < /p>
The lagrangian of the Kaluza-Klein theory\, i n its simplest five-dimensional version\, should include not only the scal ar curvature R\, but also the quadratic GaussBonnet invariant. The general lagrangian is computed and the resulting non-linear equations which genra lize Maxwell'\;s system in a quite unique way are investigated. The po ssibility of the existence of static solutions is presented\, and the qual itative behaviour of such solutions is discussed.
END:VEVENT BEGIN:VEVENT SUMMARY:Supermassive rotating boson stars in highly-asymmetric binaries: t ransient resonances and gravitational-wave observables DTSTART:20230412T110000Z DTEND:20230412T130000Z DTSTAMP:20240329T082742Z UID:ea2a7a88-c71e-461e-a06e-484cd19ef980 SEQUENCE:1 CREATED:20230410T132508Z DESCRIPTION: Abstract:The historic detection of gravitational waves paved the way for precision gravitational-wave astrophysics to blossom at unprec edented proportions. The sensitivity increment of ground-based interferome ters\, as well as the arrival of next generation space-borne detectors\, w ill unequivocally strengthen our understanding of the gravitational intera ction in extreme conditions. In this talk\, I will focus on one of the pri me targets of LISA\, the so-called extreme-mass-ratio inspirals (EMRIs). E MRIs are binaries that consist of a primary supermassive compact object\, and a stellar-mass secondary companion. Even though we are currently perfo rming pertinent tests to characterize the ``Kerrness'\;'\; of astr ophysical compact objects that reside in galactic cores\, environmental ef fects\, quantum corrections and generally multipolar deformations can sign ificantly affect the gravitational-wave emission from non-Kerr sources. In this talk\, I will discuss the rich orbital and waveform phenomenology of EMRIs as well as potential observables of fascinating effects associated with transient resonances in non-Kerr black-hole mimickers and in particul ar supermassive rotating boson stars. Finally\, I will briefly discuss the impact of exotic objects on the gravitational radiation emitted from such binaries\, that may be distinguishable with future space-based detectors\ , in order to shed more light into the electromagnetic degeneracies that c urrently exist between black holes and exotic compact objects. LAST-MODIFIED:20230410T132508Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/supermassive-rotating-boson-s tars-in-highly-asymmetric-binaries-transient-resonances-and-gravitational- wave-observables/ X-ALT-DESC;FMTTYPE=text/html: Abstract:
The
historic detection of gravitational waves paved the way for precision grav
itational-wave astrophysics to blossom at unprecedented proportions. The s
ensitivity increment of ground-based interferometers\, as well as the arri
val of next generation space-borne detectors\, will unequivocally strength
en our understanding of the gravitational interaction in extreme condition
s. In this talk\, I will focus on one of the prime targets of LISA\, the s
o-called extreme-mass-ratio inspirals (EMRIs).
EMRIs are binarie
s that consist of a primary supermassive compact object\, and a stellar-ma
ss secondary companion. Even though we are currently performing pertinent
tests to characterize the ``Kerrness'\;'\; of astrophysical compac
t objects that reside in galactic cores\, environmental effects\, quantum
corrections and generally multipolar deformations can significantly affect
the gravitational-wave emission from non-Kerr sources.
In this
talk\, I will discuss the rich orbital and waveform phenomenology of EMRIs
as well as potential observables of fascinating effects associated with t
ransient resonances in non-Kerr black-hole mimickers and in particular sup
ermassive rotating boson stars. Finally\, I will briefly discuss the impac
t of exotic objects on the gravitational radiation emitted from such binar
ies\, that may be distinguishable with future space-based detectors\, in o
rder to shed more light into the electromagnetic degeneracies that current
ly exist between black holes and exotic compact objects.
Abstract:
Supe
rnovae and stellar collisions are the sometimes incredibly luminous\, and
sometimes not so luminous\, deaths of stars that play a vital role in chem
ical enrichment\, galaxy feedback mechanisms\, and our understanding of st
ellar evolution.
Type Ia supernovae\, the explosions of white dw
arfs in binary systems\, are vital for constraining the cosmological param
eters. In this talk\, I will focus on the latest results on the progenitor
s and explosion mechanisms of Type Ia supernovae from the state-of-the-art
transient survey\, the Zwicky Transient Facility\, and describe how their
diversity may impact future precision measurements of dark energy.
I will also highlight recent advances in the related area of stellar c
ollisions\, which are testing the boundaries of current theoretical models
\, as well as discuss the link to kilonovae from neutron-star mergers (wit
h and without associated gravitational-wave detections).
Resumo
Entre vários métodos atualmente em desenvolvimento pa
ra reduzir as emissões antropogénicas de CO2 de modo a reduzir os efeito
s das alterações climáticas\, a tecnologia de Captura e Utilização de
Carbono (CCU) através plasmas não térmicos (NTPs) é bastante promisso
ra. Descargas elétricas de CO2 são estudadas atualmente\, tanto do ponto
de vista experimental como de modelização\, com o objetivo de compreend
er cinética do plasma e\, idealmente\, alcançar uma dissociação eficie
nte de CO2. Este trabalho contribui para este objetivo através de uma inv
estigação teórica\, experimental e de modelização da dissociação de
CO2 em NTPs de CO2.
Em colaboração com Laboratoire de Physiqu
e des Plasma (LPP)\, é feita uma caracterização experimental de uma des
carga luminescente DC em misturas de CO2-N2 através espectroscopia de abs
orção de infravermelho por transformada de Fourier (FTIR) como diagnóst
ico principal. Paralelamente\, foi desenvolvido um modelo autoconsistente
0D para descargas de CO2-N2 que inclui a cinética vibracional dos primeir
os 72 níveis de CO2\, 10 níveis de CO e 59 níveis de N2. Foi ainda real
izado um refinamento da cinética química do oxigénio\, motivado pela re
levância das espécies de oxigénio na cinética do plasma de CO2\, segui
do de um estudo de diferentes misturas de CO2-O2 utilizando o código num
érico Lisbon KInetics (LoKI).
O papel desempenhado pelo nível
eletronicamente excitado CO(a3Πr) em mecanismos de recombinação é resp
onsável pelo efeito prejudicial da adição de O2 na descarga. Além diss
o\, foi revelada a importância da troca vibracionaltranslacional (V-T) do
CO2-O na descrição da cinética vibracional do CO2. A partir da compara
ção entre resultados da simulação e dados experimentalmente obtidos no
LPP\, este trabalho levou ao desenvolvimento de um “mecanismo de reaç
ão” (ou seja\, um conjunto de reações e coeficientes validados experi
mentalmente).
O efeito positivo da adição de N2 na dissociaç
ão de CO2 plasmas CO2- N2 é explicado pela diluição\, limitando as rea
ções de recombinação e pelo papel de nível N2(B3Πg) no aumento da co
nversão de CO2. Finalmente\, é ainda observado que transferência de ene
rgia vibracionalvibracional (V-V) do CO2-N2 é crucial para uma descriçã
o adequada da cinética vibracional do CO2.
Detection of targe
t molecules in the air is an important task in many fields\, from safety\,
to security\, quality control\, and even medicine. There are several types
of such sensors\, optimized to different target compounds andto different
concentrations.
An artificial nose\, or e-nose\, aims to mimic
the nose of adog\, which is known to detect and recognize great number of
scents and is sensitive tominute concentrations. Ideally\, an artificial n
ose would have one sensor per targetcompound\, but clearly this is not the
case as individual sensors can respond to severalmolecules. Instead\, it
is beneficial to use approaches of artificial intelligence to find"\;f
ingerprints"\; of particular scents.
In the seminar\, I will
present our work on an e-nose that is based on capacitive sensorswith dif
ferent functionalizations. Initially\, the system was developed with the a
im ofdetecting explosives\, such as TNT and RDX. In the ongoing project\,
we are aiming atmodifying the system to detect cancer based on the exhaled
air.
Abstract:Dark energy represents perhaps the most relevant problem in cosmology.
Light scalar fields coupled to matter could explain the accelerated expans
ion of the universe. This implies going beyond Lambda-CDM and the SM\, yet
there is no observation of such fifth forces in our solar system. This di
screpancy can be resolved by a screening mechanism.
From the ple
thora of theories\, we are interested in studying the chameleon field. The
presence of this fifth interaction during the radiation-dominated era of
the universe would change the structure formation history\, alleviating so
me of the current cosmological tensions.
Moreover\, the coupling
of this field to compact objects\, such as neutron stars or white dwarves
\, affects their structure\, stability\, and dynamics\, providing us with
some hints about its detectability.
ABSTRACT: I
n non-linear electromagnetism charges come equipped with a natural screeni
ng mechanism a la K-mouflage. In this talk I will briefly review this mech
anism and discuss some phenomenological consequences of a model of dark ma
tter interacting via dark photons.
I will then discuss the linea
r response of screened charges in the context of Born-Infeld and ModMax th
eories. I will show how it is possible to construct ladder operators for t
he perturbations and how polarisability and susceptibility of certain seri
es of multiples vanish in the Born-Infeld case.
Finally\, I will
discuss how perturbation equations correspond to a supersymmetric quantum
mechanical system.
Resumo:
Atualmente\, tanto a comunidade de investigação como o
s utilizadores exigem fontes de laser capazes de fornecer impulsos de pouc
os ciclos com altas taxas de repetição\, gerados de forma eficiente\, ut
ilizando tecnologia compacta\, robusta e confiável. O uso de técnicas de
pós-compressão\, em particular alargamento espectral e compressão\,
abriu as portas para a geração de impulsos de poucos ciclos de forma efi
ciente e simples. Essa tecnologia éa base de uma nova geração de fonte
s de laser que são capazes de combinar tanto altas potências médias e i
nstantâneas\, e que melhoram as características dos impulsos\, como cont
raste temporal\, qualidade do perfile espacial e limpeza da polarização.
Nesta dissertação\, investigamos a técnica de alargamento es
pectral de multipassagem como um método de pós-compressão\, mostrando
que ela pode ser eficazmente usada em diversas montagens com energias que
variam entre alguns nanojoule atéao joule. Em particular\, um novo esqu
ema óptico édemonstrado\, capaz de contornar algumas das limitações d
as montagens anteriores e estender os limites para impulsos de energia mai
s altas. Também relatamos a primeira demonstração na faixa de energias
sub-μJ como uma alternativa aos sistemas de compressão baseados em fibra
s.
Além disso\, a técnica de multipassagens é demonstrada com
sucesso na gama de comprimentos de onda visível (515 nm)\, fornecendo\,
de forma eficiente\, impulsos de femtosegundos a partir de uma fonte infra
vermelha. Por fim\, édesenvolvido um protótipo de sistema de alargament
o espectral e édemonstrada sua aplicação para uma fonte comercial com
impulsos de um milijoule de energia. O seu desempenho e as suas caracterí
sticas são estudadas e analisadas em termos de estabilidade e qualidade d
o feixe. Um fator de compressão do impulso acima de 10 éobtido transfor
mando uma fonte de picosegundos diretamente numa fonte de femtosegundos co
m mais de 90% de eficiência\, capaz de ser usada diretamente para uma var
iedade de aplicações.
Resumo
A sumarização de fala para texto é uma técni
ca proeminente que permite economizar o tempo dispendido para acompanhar a
s notícias transmitidas diariamente. O surgimento de grandes modelos de l
inguagem a partir de aprendizagem profunda\, que têm capacidades de gera
ção de texto impressionantes\, colocou o foco da investigação em siste
mas de sumarização que produzem versões compactas e parafraseadas dos c
onteúdos de documentos\, conhecidos como resumos abstrativos.
A
modelagem de ponta-a-ponta para sumarização abstrativa de fala para tex
to é uma abordagem promissora que oferece a possibilidade de gerar repres
entações latentes ricas que aproveitam as informações não-verbais e a
cústicas do áudio\, em oposição ao simples uso de informações lingu
ísticas presentes nas transcrições geradas automaticamente em sistemas
em cascata. No entanto\, a pouca literatura sobre modelação ponta-a-pont
a desta tarefa falha em explorar diferentes domínios\, nomeadamente notí
cias.
Modelamos a sumarização de fala para texto com sistemas
em cascata e de ponta-a-ponta usando uma base de dados de notícias transm
itidas em francês. Ao contrário da literatura disponível\, a nossa nova
implementação de ponta-a-ponta faz uso de dados externos\, recorrendo
à transferência de aprendizagem de um sumarizador de texto para texto pr
é-treinado.
Experiências mostram que os resumos abstratos gera
dos pelos sistemas em cascata e de ponta-a-ponta são mais fortes do que u
ma linha de base extrativa. No entanto\, o desempenho da implementação d
e ponta-a-ponta é pior do que a implementação em cascata\, o que é obj
eto de uma extensa análise que inclui direções futuras para fechar esta
lacuna.
ABSTRACT: In this t alk\, a topological approach to determining the Hawking temperature of bla ck holes is presented\, embodied in a powerful\, covariant formula involvi ng the Euler characteristic of a (Euclideanized) spacetime manifold. This method has the advantage of allowing thermodynamical calculations to be si mply carried out on spacetimes of complicated metrical form\, as well as s hining a light on the little-known but deep links between lower-dimensiona l topology and black hole thermodynamics. The method'\;s efficacy for quantum soliton thermodynamics is also illustrated. Based on Phys. Rev. D 99\, 044042 (2019) and New J. Phys. 21\, 053042 (2019).
END:VEVENT BEGIN:VEVENT SUMMARY:Electron microscopy studies of semi-conducting materials DTSTART:20230503T143000Z DTEND:20230503T160000Z DTSTAMP:20240329T082742Z UID:31bafaed-8634-4871-8d72-bd0e87225def SEQUENCE:2 CREATED:20230421T150837Z DESCRIPTION:Boron (B) has the potential for generating an intermediate ban d in cubic silicon carbide(3C-SiC)\, turning this material into a highly e fficient absorber for single-junction solarcells. The formation of a deloc alized band demands high concentration of the foreignelement\, but the pre cipitation behavior of B in the 3C polymorph of SiC is not wellknown. Here \, probe-corrected scanning transmission electron microscopy (STEM) andsec ondary-ion mass spectrometry are used to investigate precipitation mechani sms inB-implanted 3C- SiC as a function of temperature. Point-defect clust ering was detectedafter annealing at 1273 K while stacking faults\, B-rich precipitates and dislocationnetworks developed in the 1573 - 1773 K range . The precipitates adopt therhombohedral B13C2 structure and trap B up to 1773 K. Above this temperature\,higher solubility reduces precipitation an d free B diffuses out of the implantation layer.Dopant concentrations of 1 019 at.cm−3 were achieved at 1873 K. The concept of maximizing configura tional entropy to enhance solid-state miscibilityinspires the exploration of unfamiliar composition spaces\, and the popular\, althoughimprecise\, h igh-entropy (HE) designation seems destined to endure. The spotlight hasbe en on the mechanical properties of HE alloys\, but interest in functional behavior isswiftly rising. In particular\, the vast potential of combining metal solid solutions withstructural main group elements to form HE semic onductor compounds is becomingevident. The structure of a (Zn\,Mn)(Fe\,Co\ ,Ni)Sb compound is investigated by powderX-ray diffraction\, STEM coupled to atomically resolved energy dispersive spectroscopy(EDS) and by energy-f iltered convergent-beam electron diffraction (CBED). Distinctionbetween th e 216 (half-Heusler) and 225 (full-Heusler) space groups is hindered by th esimilar scattering power of the transition metals in XRD. However\, the s tructure couldbe deciphered by STEM/EDS with the space group further attes ted by CBED. LAST-MODIFIED:20230421T151811Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/electron-microscopy-studies-o f-semi-conducting-materials/ X-ALT-DESC;FMTTYPE=text/html:Boron (B) has the p
otential for generating an intermediate band in cubic silicon carbide(3C-S
iC)\, turning this material into a highly efficient absorber for single-ju
nction solarcells. The formation of a delocalized band demands high concen
tration of the foreignelement\, but the precipitation behavior of B in the
3C polymorph of SiC is not wellknown. Here\, probe-corrected scanning tra
nsmission electron microscopy (STEM) andsecondary-ion mass spectrometry ar
e used to investigate precipitation mechanisms inB-implanted 3C- SiC as a
function of temperature. Point-defect clustering was detectedafter anneali
ng at 1273 K while stacking faults\, B-rich precipitates and dislocationne
tworks developed in the 1573 - 1773 K range.
The precipitates ad
opt therhombohedral B13C2 structure and trap B up to 1773 K. Above this te
mperature\,higher solubility reduces precipitation and free B diffuses out
of the implantation layer.Dopant concentrations of 1019 at.cm−3 were ac
hieved at 1873 K. The concept of maximizing configurational entropy to enh
ance solid-state miscibilityinspires the exploration of unfamiliar composi
tion spaces\, and the popular\, althoughimprecise\, high-entropy (HE) desi
gnation seems destined to endure. The spotlight hasbeen on the mechanical
properties of HE alloys\, but interest in functional behavior isswiftly ri
sing.
In particular\, the vast potential of combining metal soli
d solutions withstructural main group elements to form HE semiconductor co
mpounds is becomingevident. The structure of a (Zn\,Mn)(Fe\,Co\,Ni)Sb comp
ound is investigated by powderX-ray diffraction\, STEM coupled to atomical
ly resolved energy dispersive spectroscopy(EDS) and by energy-filtered con
vergent-beam electron diffraction (CBED). Distinctionbetween the 216 (half
-Heusler) and 225 (full-Heusler) space groups is hindered by thesimilar sc
attering power of the transition metals in XRD. However\, the structure co
uldbe deciphered by STEM/EDS with the space group further attested by CBED
.
Speaker: Dr Eleonora Di Valentino
Title: Challenge s to the Standard Cosmological Model
Abstr act: The Lambda Cold Dark Matter (LCDM) model has been widely accepted as the standard cosmological model due to its good agreement with a broad range of cosmological data. However\, recent studies have shown discrepan cies among the model'\;s key cosmological parameters\, which have diff erent levels of statistical significance. While some of these inconsistenc ies could be due to systematic errors\, the persistence of such tensions a cross various probes suggests a potential failure of the canonical LCDM mo del. In this seminar\, I will review the current tensions\, including the Hubble constant disagreement\, the S8 tension\, and the CMB tension\, and explore proposed solutions that could potentially alleviate them. However\ , I will also discuss the limitations of these proposed solutions and note that none of them have successfully resolved the discrepancies. Neverthel ess\, there are a few intriguing possibilities that warrant further invest igation.
END:VEVENT BEGIN:VEVENT SUMMARY:The Cosmic Ray Extremely Distributed Observatory (CREDO) DTSTART:20230503T170000Z DTEND:20230503T190000Z DTSTAMP:20240329T082742Z UID:a2edfcf7-73f7-4ac5-b967-0e011f43d414 SEQUENCE:1 CREATED:20230502T083737Z DESCRIPTION: The Cosmic Ray Extremely Distributed Observatory (CREDO) is a recently formed\,global collaboration dedicated to observing and studying cosmic ray ensembles (CRE):groups of minimum two cosmic rays with common primary interaction vertex or thesame mother particle. The CREDO program e mbraces testing the known CRE scenarios\,and getting ready to observe the unexpected physics\, it is also suitable for multimessenger and multi-miss ion applications. CRE could be formed both within classicalmodels (e.g. as products of photon-photon interactions)\, and exotic scenarios (e.g. asre sults of decay of Super Heavy Dark Matter particles and subsequent interac tions\, Lorentz invariance violation)\, their fronts might be significantl y extended in space andtime\, and they might include cosmic rays of energi es spanning the whole cosmic rayenergy spectrum. CRE are expected to be pa rtially observable on Earth even if theinitiating interaction or process o ccurs as far as ~1 Gpc away\, with a footprintcomposed of at least two ext ensive air showers with parallel arrival directions andcorrelated arrival times. Since CRE are mostly expected to be spread over large areas over hu ndreds ofkilometers or more\, and because of the expected wide energy rang e of thecontributing particles\, CRE detection might only be feasible when using the availablecosmic ray infrastructure collectively\, i.e. as a glo bally extended network of detectors.CREDO is perfectly suited for probing the variation of fundamental constants in theaforementioned physical proce sses as well as for other applications like the search forsignatures of Ea rthquake precursors within the flux of cosmic rays. LAST-MODIFIED:20230502T083737Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/the-cosmic-ray-extremely-dist ributed-observatory-credo/ X-ALT-DESC;FMTTYPE=text/html: The Cosmic Ray Ext
remely Distributed Observatory (CREDO) is a recently formed\,global collab
oration dedicated to observing and studying cosmic ray ensembles (CRE):gro
ups of minimum two cosmic rays with common primary interaction vertex or t
hesame mother particle. The CREDO program embraces testing the known CRE s
cenarios\,and getting ready to observe the unexpected physics\, it is also
suitable for multimessenger and multi-mission applications.
CRE
could be formed both within classicalmodels (e.g. as products of photon-p
hoton interactions)\, and exotic scenarios (e.g. asresults of decay of Sup
er Heavy Dark Matter particles and subsequent interactions\, Lorentz invar
iance violation)\, their fronts might be significantly extended in space a
ndtime\, and they might include cosmic rays of energies spanning the whole
cosmic rayenergy spectrum.
CRE are expected to be partially obs
ervable on Earth even if theinitiating interaction or process occurs as fa
r as ~1 Gpc away\, with a footprintcomposed of at least two extensive air
showers with parallel arrival directions andcorrelated arrival times. Sinc
e CRE are mostly expected to be spread over large areas over hundreds ofki
lometers or more\, and because of the expected wide energy range of thecon
tributing particles\, CRE detection might only be feasible when using the
availablecosmic ray infrastructure collectively\, i.e. as a globally exten
ded network of detectors.
CREDO is perfectly suited for probing t
he variation of fundamental constants in theaforementioned physical proces
ses as well as for other applications like the search forsignatures of Ear
thquake precursors within the flux of cosmic rays.
ABSTRACT: Througho
ut the Universe\, many high-energy\, cataclysmic astrophysical collisions
of neutron stars are continuously occurring. These collisions provide an e
xcellent testbed to probe the properties of supranuclear-dense matter\, to
study the production of heavy elements\, to allow for an independent meas
urement of the expansion rate of our Universe\, and to perform an indirect
search for dark matter.
Essential for such studies are reliable
models describing the merger dynamics. Keeping this in mind\, numerical-r
elativity simulations can be seen as a prerequisite for a reliable interpr
etation of multi-messenger events\, and to further develop gravitational-w
ave and electromagnetic transient models.
We show some of our mo
st recent results and identify how simulation can be used for multi-messen
ger studies and how simulations including dark matter admixed stars will o
pen the door to identify the presence of dark matter in binary neutron sta
r mergers.
Esta semana o tema de conversa do Physics@Coffee é Fluidics!
END:VEVENT BEGIN:VEVENT SUMMARY:Black hole inner horizon instability in classical and semiclassica l gravity DTSTART:20230511T143000Z DTEND:20230511T160000Z DTSTAMP:20240329T082742Z UID:9ad7ec2c-049e-46f1-9f20-b379c23fa116 SEQUENCE:1 CREATED:20230505T151044Z DESCRIPTION: ABSTRACT: In this talk I will present an overview of the inst abilities related to the presence of an inner horizon\, focusing in partic ular on the effect these can have on the evolution of the geometry as a wh ole. I will begin by presenting a simple exact model of a black hole under going the classical mass inflation process\, conveying an intuitive unders tanding of the origin of this instability\, and describing in detail the r esulting evolution of the geometry. Then I will discuss semiclassical back reaction. First\, in parallel to the Hawking evaporation of the outer hori zon\, I will analyse the semiclassical evolution of a classically unpertur bed inner horizon. Then\, I will conclude by analysing semiclassical backr eaction on a classically perturbed inner horizon (undergoing mass inflatio n)\, and discuss the possible outcomes of the evolution of a generic black hole in the full semiclassical theory. LAST-MODIFIED:20230505T151044Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/black-hole-inner-horizon-inst ability-in-classical-and-semiclassical-gravity/ X-ALT-DESC;FMTTYPE=text/html: ABSTRACT: I
n this talk I will present an overview of the instabilities related to the
presence of an inner horizon\, focusing in particular on the effect these
can have on the evolution of the geometry as a whole.
I will be
gin by presenting a simple exact model of a black hole undergoing the clas
sical mass inflation process\, conveying an intuitive understanding of the
origin of this instability\, and describing in detail the resulting evolu
tion of the geometry.
Then I will discuss semiclassical backreac
tion. First\, in parallel to the Hawking evaporation of the outer horizon\
, I will analyse the semiclassical evolution of a classically unperturbed
inner horizon. Then\, I will conclude by analysing semiclassical backreact
ion on a classically perturbed inner horizon (undergoing mass inflation)\,
and discuss the possible outcomes of the evolution of a generic black hol
e in the full semiclassical theory.
ABSTRACT: In this
talk\, I will discuss a strategy to prove the non-linear stability of the
subextremal Schwarzschild-de Sitter spacetime in the stationary region nea
r the conformal boundary. This technique is based on the extended conforma
l Einstein field equations and a conformal Gaussian gauge.
The k
ey observation is that the Cosmological stationary region of this exact so
lution can be covered by a non-intersecting congruence of conformal geodes
ics. Thus\, the future domain of dependence of suitable spacelike hypersur
faces in the Cosmological region of the spacetime can be expressed in term
s of a conformal Gaussian gauge.
A perturbative argument then al
lows proving existence and stability results close to the conformal bounda
ry and away from the asymptotic points where the Cosmological horizon inte
rsects the conformal boundary. In particular\, we show that small enough p
erturbations of initial data for the sub-extremal Schwarzschild-de Sitter
spacetime give rise to a solution to the Einstein field equations which is
regular at the conformal boundary.
ABSTRACT: Polarime
try of the light provides unique insights into multiple astrophysical proc
esses in the Universe that cannot be inferred from usual intensity observa
tions.
In this talk we review the importance of optical polarime
try in three different astrophysical systems: i) active galactic nuclei: s
upermassive black holes surrounded by accretion disks at the center of maj
or galaxies\, ii) kilonovae: the optical emission of compact neutron star
mergers that are preceded by gravitational wave emission\, and iii) supern
ovae: the explosive end of massive stars or of white dwarfs in binary syst
ems.
We discuss how different theoretical models of the progenit
or and physical processes of these systems shape the predicted optical lin
ear polarimetry and compare them to current observations. We pay particula
r attention to the systematic bias of interstellar polarization from dust
in the line of sight.
O plasma de quark e
gluões (QGP) é uma das mais intrigantes fronteiras da Física de Partí
culas. Esta forma exótica da matéria forma-se apenas em condições extr
emas\, de temperatura e densidade\, e que agora são recreáveis através
de colisões relativístas de iões pesados. O estudo deste fenómeno forn
ece informações essenciais sobre a sua extensa formulação teórica\, a
cromodinâmica quântica.
Os mesões B têm-se recentemente mos
trado extremamente relevantes para sondar o QGP\, particularmente devido a
o longo tempo de vida dos quarks b permitirem tanto registar os efeitos do
meio que atravessaram como uma reconstrução mais clara. Explorando esta
última vantagem\, ao longo desta tese são realizadas medições das sec
ções eficazes dos mesões B^+ e B_s^0 em função do momento transversal
\, p_T\, em colisões protão-protão a \\sqrt s=5.02\\ TeV. Os dados anal
isados foram adquiridos pelo detetor CMS\, durante a operação do LHC em
2017.
O sinal dos dois mesões B foram respetivamente explorados
nos canais de B_s^0\\rightarrow J/\\psi\\left(\\mu^+\\mu^-\\right)\\phi\\
left(K^+K^-\\right)\\ e B^+\\rightarrow J/\\psi(\\mu^+\\mu^-)K^+. As secç
ões eficazes medidas foram comparadas à previsão teórica FONLL e obser
vou-se uma boa concordância.
Para quantificar os efeitos do QGP
no espetro de mesões B determina-se os respetivos fatores de modificaç
ão nuclear\, R_{AA}. Em ambos os mesões observa-se uma elevada supressã
o da sua produção\, sendo os mesões B_s^0 ligeiramente menos suprimidos
que os mesões B^+.\\ \\ A baixo p_T\, o R_{AA} do mesão B_s^0 é compat
ível com a hipótese de coalescência entre quarks
Quasiperiodic syste
ms offer a myriad of fascinating phenomena\, from localization transitions
in one or higher dimensions\, to intriguing topological properties. There
has been a continued interest in these systems due to their experimental
accessibility across diverse platforms\, including ultracold atoms and tra
pped ions\, photonic and phononic media and\, more recently\, moiré mater
ials. In this seminar\, we will delve into our recent research on the quan
tum phases of both non-interacting and interacting quasiperiodic systems.<
br/>
We will start by introducing a theoretical framework that we hav
e developed to characterize the localization phase diagrams of non-interac
ting 1D quasiperiodic systems\, that includes extended\, localized\, and e
ven critical multifractal phases. This theory\, based on a renormalization
-group procedure\, allowed us to connect widely different models in the li
terature and in some cases\, fully analytically characterize the phase dia
grams. We will then generalize our theory to interacting quasiperiodic sys
tems.
By applying this generalization to a broad class of 1D qua
siperiodic chains\, we will unveil a compelling finding: short-range inter
actions become irrelevant in the vicinity of ground-state localization-del
ocalization transitions. Finally\, we will explore the role of quasiperiod
icity in moiré systems. Through illustrative examples\, we will demonstra
te that quasiperiodicity can be of crucial importance\, being responsible
for creating non-trivial states of matter\, inaccessible in the periodic c
ase.
ABSTRACT: Gravitat ional-wave and multi-messenger astronomy shed light on the astrophysics of black-holes and neutron-stars and also allow for unique probes of fundame ntal physics. I will discuss recent results on how the mergers of neutron stars as well as other explosive systems such as the death of massive\, ro tating stars give rise to the formation of heavy elements in the universe. In particular\, I will discuss recent results at the interface of numeric al relativity\, relativistic astrophysics\, neutrino physics\, and nuclear astrophysics\, and highlight how multi-messenger astronomy may lead to th e answer of a 70-year old fundamental question in physics: How does the Un iverse create the heaviest elements?
END:VEVENT BEGIN:VEVENT SUMMARY:Let's talk about... Burning fusion plasmas DTSTART:20230525T170000Z DTEND:20230525T190000Z DTSTAMP:20240329T082742Z UID:b1d0eba1-7085-43f5-9064-49ebfa483b6c SEQUENCE:1 CREATED:20230520T174226Z DESCRIPTION: LAST-MODIFIED:20230520T174226Z LOCATION: URL:http://df.vps.tecnico.ulisboa.pt/eventos/lets-talk-about-burning-fusio n-plasmas/ END:VEVENT BEGIN:VEVENT SUMMARY:Towards Quantum Simulation of Bound States Scattering DTSTART:20230530T143000Z DTEND:20230530T160000Z DTSTAMP:20240329T082742Z UID:b85fd4c2-b89e-458d-a4e5-9142a3c9052f SEQUENCE:1 CREATED:20230525T092909Z DESCRIPTION: The last years have seen a rapid development of applications of quantum computationto quantum field theory. The first quantum algorithm s for simulation of scattering havebeen proposed in the context of scalar and fermionic theories\, requiring thousands oflogical qubits. These algor ithms are not suitable to simulate scattering of incomingbound states\, as the initial state preparation relies typically on adiabaticallytransformi ng wavepackets of the free theory into wavepackets of the interactingtheor y.In this talk\, I will present a strategy to excite wavepackets of the in teractingtheory directly from the vacuum of the interacting theory\, allow ing for preparation ofstates of composite particles that can be taken as i nitial states of a scatteringsimulation. This is the first step towards di gital quantum simulation of scattering ofbound states. The approach is bas ed on the Haag-Ruelle scattering theory\, whichprovides a way to construct creation and annihilation operators of a quantum fieldtheory in a full\, nonperturbative framework. To show that the idea works for quantumcomputat ion\, I will describe a quantum algorithm implementing the approach. LAST-MODIFIED:20230525T092909Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/towards-quantum-simulation-of -bound-states-scattering/ X-ALT-DESC;FMTTYPE=text/html: The last years hav
e seen a rapid development of applications of quantum computationto quantu
m field theory. The first quantum algorithms for simulation of scattering
havebeen proposed in the context of scalar and fermionic theories\, requir
ing thousands oflogical qubits.
These algorithms are not suitabl
e to simulate scattering of incomingbound states\, as the initial state pr
eparation relies typically on adiabaticallytransforming wavepackets of the
free theory into wavepackets of the interactingtheory.In this talk\, I wi
ll present a strategy to excite wavepackets of the interactingtheory direc
tly from the vacuum of the interacting theory\, allowing for preparation o
fstates of composite particles that can be taken as initial states of a sc
atteringsimulation.
This is the first step towards digital quant
um simulation of scattering ofbound states. The approach is based on the H
aag-Ruelle scattering theory\, whichprovides a way to construct creation a
nd annihilation operators of a quantum fieldtheory in a full\, nonperturba
tive framework. To show that the idea works for quantumcomputation\, I wil
l describe a quantum algorithm implementing the approach.
Dynamical quantum
phase transitions (DQPTs) are defined by the non-analyticity intime in the
Loschmidt echo\, which measures the overlap between the time-evolvedstate
and the initial state when a system is brought out of equilibrium. While
the studyof DQPTs has been thriving\, how the system behaves around the cr
itical time remainsan open question.
In this talk\, we will expl
ore the dynamics of the many-body systemsaround DQPT using various probes.
We find that the extrema in the time evolutionof the equilibrium order pa
rameter are connected to DQPTs in the Su-SchreifferHeeger model. We will a
lso discuss how the correlations spread under the influence ofinter and in
tra- cell interactions in the model as probed by unequal time Greenfunctio
ns.
The concept of Loschmidt amplitude spectrum – an extension
of theLoschmidt echo measures will also be introduced. The spectrum sugge
sts there is apopulation redistribution in the momentum space across the t
ransition in thequantum Ising model\, providing us new insight into the be
haviour of the systemaround DQPTs.
Title: Spin Textures and Spin Waves
Speaker: Prof. Daniela Petti (Politecnico di Milano)
Abs tract:
Spin textures are nonuniform confi gurations in the arrangement of spins in magnetic materials\, which are ra ising interest as active components in data storage and signal processing. During this lecture\, different spin textures\, such as domain walls\, vo rtices and skyrmions\, will be introduced and their main applications will be discussed. We will also examine different lithographic approaches to s tabilize spin textures\; indeed spin textures are stable\, have a high deg ree of tunability and have nanoscale dimensions. In the second part of the lecture\, spin waves will be introduced. They are propagating perturbatio n in the spin lattice of ordered magnetic materials. In analogy to photoni cs\, magnonics uses spin waves to carry and process information at the GHz -THz frequency\, but differently\, the typical wavelength of spin waves at these frequencies is in the nanometer range\, while the wavelength of ele ctromagnetic radiation is order of magnitude longer. Currents of magnons\, the equivalent quanta of spin waves\, can carry energy (frequency) and an gular momentum (spin) without motion of charges\, which makes them promisi ng for beyond CMOS computing\, due to the absence of Joule heating. We wil l finally explore the interaction of the spin textures with the spin waves \, focusing on how spin textures can be used to manipulate spin waves at t he nanoscale. Some example will be discussed.
END:VEVENT BEGIN:VEVENT SUMMARY:Numerical relativity and semi-analytical waveforms for the fourth observing run of the LIGO-Virgo-KAGRA detectors DTSTART:20230601T143000Z DTEND:20230601T160000Z DTSTAMP:20240329T082742Z UID:86ccbac8-c801-4e1d-8066-4d2dbdff258f SEQUENCE:2 CREATED:20230526T105032Z DESCRIPTION:ABSTRACT: The successful observation campaigns by the global g ravitational wave detectors network and the expectation of hundreds of new systems detected in the upcoming observation run\, O4\, starting on May 2 023\, are paving the way for the detection of GW events with challenging p hysical properties. Particularly\, the large number of expected detections of binary black holes in O4 may lead to clear detection of orbital eccent ricity and spin-precession\, which would provide key information about the formation channels of such binaries. However\, so far the waveform models used by the community\, including the LIGO\, Virgo and Kagra collaboratio ns\, to detect and estimate the parameters of the gravitational wave signa ls assume quasi-circular orbits or non spin-precessing binaries. In this p resentation\, I will describe the current status of ready-to-use quasi-cir cular waveform models for O4\, as well as current efforts to model the gra vitational signal from generic binary black holes\, including the producti on of accurate eccentric numerical relativity simulations and some of thei r applications\, such as comparisons with small mass ratio perturbation th eory results to bridge the gap between comparable masses and extreme mass ratio systems in elliptical orbits. LAST-MODIFIED:20230526T105105Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/numerical-relativity-and-semi -analytical-waveforms-for-the-fourth-observing-run-of-the-ligo-virgo-kagra -detectors/ X-ALT-DESC;FMTTYPE=text/html:ABSTRACT: Th
e successful observation campaigns by the global gravitational wave detect
ors network and the expectation of hundreds of new systems detected in the
upcoming observation run\, O4\, starting on May 2023\, are paving the way
for the detection of GW events with challenging physical properties.
Particularly\, the large number of expected detections of binary bla
ck holes in O4 may lead to clear detection of orbital eccentricity and spi
n-precession\, which would provide key information about the formation cha
nnels of such binaries.
However\, so far the waveform models use
d by the community\, including the LIGO\, Virgo and Kagra collaborations\,
to detect and estimate the parameters of the gravitational wave signals a
ssume quasi-circular orbits or non spin-precessing binaries.
In
this presentation\, I will describe the current status of ready-to-use qua
si-circular waveform models for O4\, as well as current efforts to model t
he gravitational signal from generic binary black holes\, including the pr
oduction of accurate eccentric numerical relativity simulations and some o
f their applications\, such as comparisons with small mass ratio perturbat
ion theory results to bridge the gap between comparable masses and extreme
mass ratio systems in elliptical orbits.
ABSTRACT: We consid
er coupled dark energy (CDE) cosmologies\, where dark matter particles fee
l a force stronger than gravity\, due to the fifth force mediated by a sca
lar field which plays the role of dark energy. We perform for the first ti
me a tomographic analysis of coupled dark energy\, where the coupling stre
ngth is parametrized and constrained in different redshift bins. This allo
ws us to verify which data can better constrain the strength of the coupli
ng and how large the coupling can be at different epochs.
First\
, we employ cosmic microwave background data from Planck\, the Atacama Cos
mology Telescope (ACT) and South Pole Telescope (SPT)\, showing the impact
of different choices that can be done in combining these datasets. Then\,
we use a range of low redshift probes to test CDE cosmologies\, both for
a constant and for a tomographic coupling.
In particular\, we us
e for the first time data from weak lensing (the KiDS-1000 survey)\, galax
y clustering (BOSS survey)\, and their combination\, including 3x2pt galax
y-galaxy lensing crosscorrelation data. We do not find evidence for nonzer
o coupling\, either for a constant or tomographic case. A nonzero coupling
is however still in agreement with current data.
For CMB and ba
ckground datasets\, a tomographic coupling allows for β values up to one
order of magnitude larger than in previous works\, in particular at z<\;
1. The use of 3x2pt analysis then becomes important to constrain β at low
redshifts\, even when coupling is allowed to vary: for 3x2pt we find\, at
0.5
We study the quant
um and semiclassical dynamics of the dissipative SU(3) BoseHubbard trimer
model. By setup non-cyclic and cyclic limits\, we could study thegapped an
d gapless Liouvilian spectrum and the dynamics of steady states. Employing
exact diagonalization on the quantum Liouvillian superoperator and steady-
statedensity matrix\, we characterize quantum chaos through the level stat
istics of theireigenvalues.
The gapped case exhibits a unique we
ll-defined steady state\, while thegapless one possesses multiple steady s
tates with regular\, limit cycles and chaotictrajectories. The spacing lev
el statistics of the density matrix associated with a unique steady stateo
r regular trajectories is a Poisson\, while for chaotic multiples steady s
tates thedistribution is Gaussian Unitary Ensemble.
From the sem
i-classical point of view\, we obtained the equations of motion by astanda
rd Keldysh path integral method together with the proper stochastic Langev
inequation. We show robust evidence pointing out a deep connection between
thequantum-level statistics of the density matrix and the distribution of
Lyapunovexponents associated with classical trajectories for long times.
Title: Explo ring and the Low Surface Brightness Universe with Deep Imaging
Speaker: Prof. Pierre-Alain Duc
Abstract:
The exploration of the Low Surface Brightness (LSB) Universe currently motivates several s urveys across the world\, carried out with a number of instruments\, and provides observational constrains for numerical simulations. It impacts multiple scientific fields\, including the ISM structure\, galaxy formati on and evolution and cosmology\, and has generated passionate debates\, fo r instance regarding the very existence\, nature and properties of the so called Ultra-Diffuse-Galaxies. Meanwhile the community prepares for the exploitation of next generation surveys\, including Euclid and LSST.
I will review the current efforts done by our group in this active field of science and will in particular focus on what deep imaging can tell us about the way galaxies have assembled their mass through mergers.
END:VEVENT BEGIN:VEVENT SUMMARY:Effects of Disorder in Higher-order Topological Insulators DTSTART:20230609T133000Z DTEND:20230609T150000Z DTSTAMP:20240329T082742Z UID:f44a5105-6920-4a87-8a34-f2f29a372215 SEQUENCE:2 CREATED:20230607T102613Z DESCRIPTION:Resumo:Isolantes topológicos são materiais com propriedades topológicas exóticas protegidas por simetrias\, que foram recentemente g eneralizados para ordem superior. Tendo em conta que desordem ocorre em qu alquer implementação prática\, é importante compreender como afecta es tes sistemas. Neste trabalho\, aplicamos desordem que preserva a simetria quiral aos modelos prototípicos de Bernalcazar-Bernevig-Hughes (BBH) para isolantes topológicos de ordem superior. Revemos os invariantes topológ icos dos sistemas limpos\, com o método dos nested Wilson loops no espaç o recíproco. Estudamos um sistema 2D desordenado\, encontrando-se um isol ante topológico de Anderson de segunda ordem (SOTAI) induzido por desorde m\, com momento quadropular quantizado\, em fases com e sem gap. Com o aum ento de desordem\, o sistema transita para um regime de Griffiths de compo rtamento multifractal\, seguido de um isolante de Anderson trivial. Os res ultados centrais são a 3D\, onde encontramos o primeiro exemplo de um iso lante topológico de Anderson de terceira ordem (TOTAI)\, com momento octu polar quantizado. Para desordem mais intensa\, o TOTAI transita para um me tal difusivo trivial\, tornando-se um isolante de Anderson a desordem aind a superior. Os resultados são apoiados por uma análise numérica exata e detalhada\, revelando também estados protegidos localizados nos cantos\, tanto em 2D como em 3D. Em 3D\, a transição induzida por desordem para a fase TOTAI também se capta analiticamente com precisão notável utiliz ando a aproximação auto-consistente de Born. Os nossos resultados demons tram que desordem pode induzir fases topológicas de terceira ordem em 3D\ , aumentando assim a classe de isolantes de Anderson topológicos de ordem superior conhecidos. LAST-MODIFIED:20230609T105859Z LOCATION:Anfiteatro VA1\, Pavilhão de Civil/ Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/effects-of-disorder-in-higher -order-topological-insulators/ X-ALT-DESC;FMTTYPE=text/html:Resumo:
< p data-block-key="bko1f">Isolantes topológicos são materiais com proprie dades topológicas exóticas protegidas por simetrias\, que foram recentem ente generalizados para ordem superior. Tendo em conta que desordem ocorre em qualquer implementação prática\, é importante compreender como afe cta estes sistemas. Neste trabalho\, aplicamos desordem que preserva a sim etria quiral aos modelos prototípicos de Bernalcazar-Bernevig-Hughes (BBH ) para isolantes topológicos de ordem superior. Revemos os invariantes to pológicos dos sistemas limpos\, com o método dos nested Wilson loops< /i> no espaço recíproco.Abstract: Sp in-orbit coupling (SOC)—a relativistic interaction which entangles a par ticle’s motion with its quantum mechanical spin—is fundamental to a wi de range of physical phenomena\, spanning from the formation of topologica l insulators to the spin Hall effect of light. Recent years have seen rema rkable progress in the probing\, enhancing and tailoring of SOC in artific ial materials\, specifically heterostructures\, made of two or more indivi dual flakes of graphene-like crystals arranged in a stack. From the electr ical control of spin-valley coupling in bilayer graphene [1]\, to the reve rsible spin-charge conversion in graphene with proximity-induced SOC court esy of atomically-thin semiconductors [2]\, these discoveries challenge ou r previous notions on the possible behaviour of spin-orbit coupled electro ns at hetero-interfaces.
In this talk\, I will show that the rich array of spin-dependent phenomena facilitated by proximity-induced SOC in graphene can be underst ood from the perspective of quantum information theory\, i.e.\, as arising from quantum-mechanical entanglement between real spin and lattice-pseudo spin degrees of freedom [3]. The proximity-induced SOC
and ensuing spin-spin entanglement are sensitive to the atomic r egistry between graphene and its high-SOC partner material\, which opens u p interesting possibilities for spin-charge interconversion\, including a current-induced spin polarization tuneable by means of a simple interlayer rotation angle [4].
References:
[1] “Anisotropic spi n currents in graphene”\, https://physics.aps.org/articles/v11/s108
< p data-block-key="60g2n">[2] “Proposal for unambiguous electrical detect ion of spin-charge conversion in lateral spin valves”\, S. Cavill\, C. H uang\, M. Offidani\, Y.-H. Lin\, M. Cazalilla and A. Ferreira\, Phys. Rev. Lett. 124 (2020).[3] “Theory of spin-char ge-coupled transport in proximitized graphene: an SO(5) algebraic approach ”\, A. Ferreira\, J. Phys. Mater. 4\, 045006 (2021).
[4] “Twist angle controlled collinear Edelstein effect in van der Waals heterostructures”\, A. Veneri\, D. Perkins\, C. Péterfalvi an d A. Ferreira\, Phys. Rev. B 106\, L081405 (2022).
END:VEVENT BEGIN:VEVENT SUMMARY:Vector-like quarks of Nelson-Barr type: an overview DTSTART:20230615T110000Z DTEND:20230615T130000Z DTSTAMP:20240329T082742Z UID:17be8d5c-11f2-4609-9176-c16d1d6616e3 SEQUENCE:1 CREATED:20230606T141800Z DESCRIPTION: Abstract:The Nelson-Barr mechanism to solve the strong CP pro blem requires vector-like quarks (VLQs) to transmit the spontaneous CP bre aking to the SM. Even in the scenario where the spontaneous CP breaking se ctor is inaccessible\, these VLQs can be at the TeV scale in reach at pres ent colliders. In this talk I will show how these VLQs of Nelson-Barr type differ from generic VLQs and find from parameter counting that one less p arameter is needed. In particular\, for one VLQ of Nelson-Barr type\, ther e is only one CP odd quantity that is responsible for all CP violation in the quark sector. In this case\, I will show that the model is largely fla vor safe. A global fit on the relevant flavor observables is also performe d\, and a comparison is made to the case of one generic VLQ. We find that the allowed parameter space for the VLQ Yukawa couplings and the mixing to the SM are confined to a region much smaller than in the generic case\, m aking the NB case falsifiable in principle. I conclude presenting some rec ent analyses for the case in which two VLQs (either of down or up-type) ar e considered at the same time. LAST-MODIFIED:20230606T141800Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/vector-like-quarks-of-nelson- barr-type-an-overview/ X-ALT-DESC;FMTTYPE=text/html:
Abstract:
The Nelson-Barr mechani
sm to solve the strong CP problem requires vector-like quarks (VLQs) to tr
ansmit the spontaneous CP breaking to the SM. Even in the scenario where t
he spontaneous CP breaking sector is inaccessible\, these VLQs can be at t
he TeV scale in reach at present colliders.
In this talk I will
show how these VLQs of Nelson-Barr type differ from generic VLQs and find
from parameter counting that one less parameter is needed. In particular\,
for one VLQ of Nelson-Barr type\, there is only one CP odd quantity that
is responsible for all CP violation in the quark sector. In this case\, I
will show that the model is largely flavor safe.
A global fit on
the relevant flavor observables is also performed\, and a comparison is m
ade to the case of one generic VLQ. We find that the allowed parameter spa
ce for the VLQ Yukawa couplings and the mixing to the SM are confined to a
region much smaller than in the generic case\, making the NB case falsifi
able in principle. I conclude presenting some recent analyses for the case
in which two VLQs (either of down or up-type) are considered at the same
time.
ABSTRACT: G
R-Athena++ is a general-relativistic\, high-order\, vertex-centered solver
that extends the oct-tree\, adaptive mesh refinement capabilities of Athe
na++. Dynamical spacetimes are simulated using the Z4c formulation of nume
rical relativity coupled to the moving puncture gauge. Robust and accurate
binary black hole (BBH) mergers are demonstrated.
GR-Athena++ l
everages the task-based parallelism paradigm of Athena++ to achieve excell
ent scalability. Strong scaling efficiencies above 95% for up to 1.2×1e4
CPUs and excellent weak scaling up to 1e5 CPUs are measured for production
BBH runs. GR-Athena++ provides infrastructure for the robust simulation o
f compact binary coalescences and offers a viable path towards numerical r
elativity at exascale.
In this talk\, a general overview of feat
ures outlined above will be provided. Recent developments will also be dis
cussed together with our incorporation of compact finite differencing for
vacuumsector evolution.
ABSTRACT: Superflu id dark matter is a novel way of reconciling the apparent discrepancy betw een galactic phenomenology and LCDM cosmology. The advantage of these mode ls is that on cosmological scales they can play the role of CDM\, while on galactic scales there is a phase transition to a superfluid\, and the non trivial dynamics in this regime can reproduce the observed Tully-Fisher re lation.
Howeve r\, we find in general these models exhibit a breakdown of causality\, whi ch indicates they would resist having any standard UV completion. Construc ting a class of causal k-essence theories\, instead of dark matter we can consider these as scalar modifications of gravity.
In these theories the strength of the new force grows with increasing density\, becoming most relevant in the d ensest astrophysical environments. We consider various observational const raints on this class of modified gravity theories\, with the strongest con straint coming from equilibrium of neutron stars.
END:VEVENT BEGIN:VEVENT SUMMARY:Thermodynamics of black holes and self-gravitating hot matter DTSTART:20230621T140000Z DTEND:20230621T160000Z DTSTAMP:20240329T082742Z UID:57a18aa7-dc44-41b7-aa79-d05cb48ee7e6 SEQUENCE:2 CREATED:20230619T095349Z DESCRIPTION: Abstract: Black holes and self-gravitating hot matter can be viewed as thermodynamic objects. This fact reveals the existence of a lin k between thermodynamics and gravitation\, since at a fundamental level th ermodynamics stems from the quantum behavior of the systems. The essence o f the connection is still unknown\, but it is indicated that comes from th e quantum character of gravitation. To shed light on the nature of this li nk\, it is essential to analyze the thermodynamic properties of curved spa cetime with black holes and self-gravitating matter together. It is also i nteresting to generalize the analysis to higher dimensions\, in connection with theories of quantum gravity that require dimensions higher than four . In this seminar\, I will mainly focus on two works: I will present the t hermodynamic properties of a charged spherical hot thin shell in higher di mensions\, by imposing the first law of thermodynamics\, showing its entro py and its thermodynamic stability\, where suggestive equations of state h ave been chosen for the shell\, clarifying thus the contributions of the s elf-gravitating nature of ordinary matter to the entropy and other thermod ynamic quantities\; I will also present the grand canonical ensemble of a d-dimensional charged black hole in a cavity\, through the Euclidean path integral approach in the zero loop approximation\, which has two solutions for the horizon radius of the black hole\, where the solution with the la rgest radius is stable. In addition\, I will present the ongoing work on t he canonical ensemble of charged black holes in acavity\, the canonical e nsemble for pure self-gravitating hot matter shells\, and the grand canoni cal ensemble of black holes and matter shells\, as well as other recent pr ojects. LAST-MODIFIED:20230619T104415Z LOCATION:Sala de Formação Avançada do DF (Sala 2-8.11 - 2º Piso do Pav ilhão de Física) URL:http://df.vps.tecnico.ulisboa.pt/eventos/thermodynamics-of-black-holes -and-self-gravitating-hot-matter/ X-ALT-DESC;FMTTYPE=text/html:
Abstract:
Black holes and
self-gravitating hot matter can be viewed as thermodynamic objects. This
fact reveals the existence of a link between thermodynamics and gravitatio
n\, since at a fundamental level thermodynamics stems from the quantum beh
avior of the systems. The essence of the connection is still unknown\, but
it is indicated that comes from the quantum character of gravitation. To
shed light on the nature of this link\, it is essential to analyze the the
rmodynamic properties of curved spacetime with black holes and self-gravit
ating matter together.
It is also interesting to generalize the
analysis to higher dimensions\, in connection with theories of quantum gra
vity that require dimensions higher than four. In this seminar\, I will ma
inly focus on two works: I will present the thermodynamic properties of a
charged spherical hot thin shell in higher dimensions\, by imposing the fi
rst law of thermodynamics\, showing its entropy and its thermodynamic stab
ility\, where suggestive equations of state have been chosen for the shell
\, clarifying thus the contributions of the self-gravitating nature of ord
inary matter to the entropy and other thermodynamic quantities\; I will al
so present the grand canonical ensemble of a d-dimensional charged black h
ole in a cavity\, through the Euclidean path integral approach in the zero
loop approximation\, which has two solutions for the horizon radius of th
e black hole\, where the solution with the largest radius is stable.
In addition\, I wil l present the ongoing work on the canonical ensemble of charged black hole s in acavity\, the canonical ensemble for pure self-gravitating hot matte r shells\, and the grand canonical ensemble of black holes and matter shel ls\, as well as other recent projects.
END:VEVENT BEGIN:VEVENT SUMMARY:Integration algorithms for charged-particle dynamics in magnetised plasmas DTSTART:20230622T090000Z DTEND:20230622T110000Z DTSTAMP:20240329T082742Z UID:07da0bca-36bb-49b3-b802-8a8e3a7de3d4 SEQUENCE:2 CREATED:20230620T143743Z DESCRIPTION:Resumo:Neste projeto de tese\, a validade do modelo centro-gui a (CG) foi testada a partir da comparação entre as trajetórias de órbi ta completa (OC) e de CG de alfas de fusão em configurações magnéticas complexas típicas de dispositivos de fusão.Para realizar as integraçõ es OC\, a funcionalidade da biblioteca \\textsc{gyronimo} foi estendida co m o sistema dinâmico da força de Lorentz em coordenadas curvilíneas e o utros algoritmos. Três integradores FO foram comparados: Boris Clássico\ , Boris Curvilíneo e Runge-Kutta de 4ª ordem. Com base nas propriedades de conservação das constantes de movimento dos algoritmos e no formato d a trajetória em campos eletromagnéticos simples em coordenadas toroidais \, o método numérico mais preciso para integrações longas foi escolhid o para as subsequentes integrações OC.Em seguida\, diversos casos de ór bitas de alfas obtidas por integrações OC e CG no equilíbrio magnético estático de um tokamak axissimétrico e de um stellarator não-axissimé trico foram comparados. Demonstra-se que\, apesar de os resultados OC e CG concordarem para o equilíbrio tokamak\, há casos em que as abordagens d iscordam nos campos magnéticos 3D mais complexos de um dispositivo stella rator.Para determinar a relevância das discrepâncias nas órbitas OC e C G no equilíbrio stellarator escolhido\, foi implementada e executada uma simulação do confinamento de partículas alfas de fusão\, onde se verif icou que a abordagem OC previa mais do dobro de alfas perdidos que a abord agem CG. Além disso\, verificou-se que as alfas são perdidas na mesma re gião para ambos tipos de integração\, mas distribuídas de forma difere nte no interior da mesma. LAST-MODIFIED:20230620T143810Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/integration-algorithms-for-ch arged-particle-dynamics-in-magnetised-plasmas/ X-ALT-DESC;FMTTYPE=text/html:Resumo:
Neste projeto de te
se\, a validade do modelo centro-guia (CG) foi testada a partir da compara
ção entre as trajetórias de órbita completa (OC) e de CG de alfas de f
usão em configurações magnéticas complexas típicas de dispositivos de
fusão.
Para realizar as integraç
ões OC\, a funcionalidade da biblioteca \\textsc{gyronimo} foi estendida
com o sistema dinâmico da força de Lorentz em coordenadas curvilíneas e
outros algoritmos. Três integradores FO foram comparados: Boris Clássic
o\, Boris Curvilíneo e Runge-Kutta de 4ª ordem. Com base nas propriedade
s de conservação das constantes de movimento dos algoritmos e no formato
da trajetória em campos eletromagnéticos simples em coordenadas toroida
is\, o método numérico mais preciso para integrações longas foi escolh
ido para as subsequentes integrações OC.
Em seguida\, diversos casos de órbitas de alfas obtidas por integ
rações OC e CG no equilíbrio magnético estático de um tokamak axissim
étrico e de um stellarator não-axissimétrico foram comparados. Demonstr
a-se que\, apesar de os resultados OC e CG concordarem para o equilíbrio
tokamak\, há casos em que as abordagens discordam nos campos magnéticos
3D mais complexos de um dispositivo stellarator.
Para determinar a relevância das discrepâncias nas órbitas OC e CG no equilíbrio stellarator escolhido\, foi implementada e executa da uma simulação do confinamento de partículas alfas de fusão\, onde s e verificou que a abordagem OC previa mais do dobro de alfas perdidos que a abordagem CG. Além disso\, verificou-se que as alfas são perdidas na m esma região para ambos tipos de integração\, mas distribuídas de forma diferente no interior da mesma.
END:VEVENT BEGIN:VEVENT SUMMARY:Scalar field solutions in the Weyl class DTSTART:20230622T143000Z DTEND:20230622T160000Z DTSTAMP:20240329T082742Z UID:fc7fb08b-3d5c-4fd1-b99f-0d908f1ff730 SEQUENCE:1 CREATED:20230616T110244Z DESCRIPTION: ABSTRACT: After briefly reviewing the properties of the Weyl- scalar field system we derive and analyze a particularly simple phantom sc alar field solution within the Weyl geometry (a natural counterpart of the Curzon--Chazy spacetime). We show that this solution contains a wormhole throat which connects to a region that is not asymptotically flat and that behaves like a one-directional time machine. We investigate its conformal structure and analyze a non-scalar singularity appearing beyond the wormh ole throat. Various definitions of mass of the spacetime are compared in t he presence of phantom matter. LAST-MODIFIED:20230616T110244Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/scalar-field-solutions-in-the -weyl-class/ X-ALT-DESC;FMTTYPE=text/html:ABSTRACT: After br iefly reviewing the properties of the Weyl-scalar field system we derive a nd analyze a particularly simple phantom scalar field solution within the Weyl geometry (a natural counterpart of the Curzon--Chazy spacetime).
We show that this solution contains a wormhole throat which connects to a region that is not asymptotically flat and that behaves like a one-directional time machine. We investigate its conformal structure and analyze a non-scalar singulari ty appearing beyond the wormhole throat. Various definitions of mass of th e spacetime are compared in the presence of phantom matter.
END:VEVENT BEGIN:VEVENT SUMMARY:Tidal deformability of gravitational atoms DTSTART:20230623T140000Z DTEND:20230623T160000Z DTSTAMP:20240329T082742Z UID:68e7a0de-e0e2-4e62-9928-b5011cc63ba2 SEQUENCE:1 CREATED:20230621T082211Z DESCRIPTION: Resumo: Na última década\, a deteção de ondas gravitacion ais (OG) provou ser uma ferramenta útil para estudar objetos astrofísico s\, nomeadamente sistemas com um campo gravítico forte como os buracos ne gros (BNs). Espera-se que esta revele utilidade experimental para os model os de extensão do Modelo Padrão como a natureza de partículas ultraleve s e Matéria Escura. Se existirem campos bosonicos ultraleves em torno de BNs\, o processo de superradiância\, que é um mecanismo de amplificaçã o de ondas\, pode levar a uma instabilidade que causa o seu crescimento ex ponencial em amplitude e extrai massa e momento angular do BN até que se forme um condensado (ou nuvem) que roda com o BN. Esta nuvem depois emite sinais de OGs que podem ser analisados e transmitir conhecimento em relaç ão a nova física. Nesta tese focamo-nos na deformabilidade de maré dest es BNs "\;vestidos"\; com um campo escalar através do cálculo de alguns dos seus números de Love de maré (NLM). Estes coeficientes quant ificam a resposta induzida na estrutura multipolar de um objeto devido à sua interação gravítica com outro corpo maciço. Fazemos isto nas aprox imações de limite Newtoniano\, onde se assume que o campo gravítico é fraco e os objetos têm velocidades baixas\, e de pequeno-acoplamento (ent re o campo escalar e o BN). Visto que foi provado que os BNs têm NLM nulo s\, qualquer deteção de OGs cuja assinatura implique NLM não-nulos pode indicar a existência de partículas ultraleves. LAST-MODIFIED:20230621T082211Z LOCATION:Sala P12 Pavilhão de Matemática\, Piso 2 URL:http://df.vps.tecnico.ulisboa.pt/eventos/tidal-deformability-of-gravit ational-atoms/ X-ALT-DESC;FMTTYPE=text/html:Resumo:
Na última década\, a deteção de ondas gravitaciona
is (OG) provou ser uma ferramenta útil para estudar objetos astrofísicos
\, nomeadamente sistemas com um campo gravítico forte como os buracos neg
ros (BNs). Espera-se que esta revele utilidade experimental para os modelo
s de extensão do Modelo Padrão como a natureza de partículas ultraleves
e Matéria Escura.
Se existirem campos bosonicos ultraleves em
torno de BNs\, o processo de superradiância\, que é um mecanismo de ampl
ificação de ondas\, pode levar a uma instabilidade que causa o seu cresc
imento exponencial em amplitude e extrai massa e momento angular do BN at
é que se forme um condensado (ou nuvem) que roda com o BN. Esta nuvem dep
ois emite sinais de OGs que podem ser analisados e transmitir conhecimento
em relação a nova física.
Nesta tese focamo-nos na deformabi
lidade de maré destes BNs "\;vestidos"\; com um campo escalar atr
avés do cálculo de alguns dos seus números de Love de maré (NLM). Este
s coeficientes quantificam a resposta induzida na estrutura multipolar de
um objeto devido à sua interação gravítica com outro corpo maciço. Fa
zemos isto nas aproximações de limite Newtoniano\, onde se assume que o
campo gravítico é fraco e os objetos têm velocidades baixas\, e de pequ
eno-acoplamento (entre o campo escalar e o BN). Visto que foi provado que
os BNs têm NLM nulos\, qualquer deteção de OGs cuja assinatura implique
NLM não-nulos pode indicar a existência de partículas ultraleves.
Abstract:he Teukolsky master equations describe the gauge invariant degrees of f
reedom in linear gravitational perturbations of the Kerr black hole family
.
In this talk\, we focus on separable solutions to the Teukolsky equa
tions\, for which superradiance and trapping phenomena can be understood.
Particular emphasis will be given to mode stability\, that is non-existenc
e of exponentially growing or bounded but non-decaying separable solutions
.
A corollary of our analysis is that general solutions to the T
eukolsky equations are bounded and decay in time\; this is a key first ste
p in establishing (linear) stability of Kerr black holes.
This talk co
ntains joint work with Marc Casals (Leipzig/CBPF/UC Dublin) and Yakov Shla
pentokh-Rothman (Toronto).
Abstract:
The combination of precise determinations of $V_{u
s}$ and $V_{ud}$ hints towards a violation of the CKM first row unitarity
at about $3\\sigma$ level. A possible explanation can be the mixing of SM
quarks with vector-like quarks\, up or down type $SU(2)_L$ singlets or
$SU(2)_L$ doublet\, with mass of few TeV\, having large enough mixings wi
th the lighter quarks. A different solution may come from the introductio
n of the gauge horizontal family symmetry acting between the lepton famili
es and spontaneously broken at the scale of about 6 TeV.
Anothe
r tension in the value of the Cabibbo angle is also reported at $3\\sigma$
level\, between two determinations of $V_{us}$ obtained from semi-leptoni
c and leptonic kaon decays. A vector-like doublet can account for this di
screpancy. Although one extra multiplet cannot entirely explain all the C
abibbo anomalies\, a combination such as two species of isodoublets\, or o
ne isodoublet and up or/and down type isosinglet can be a complete solutio
n.
Moreover\, the recent measurement of
the $W$-boson mass by the CDF Collaboration exhibits significant tension w
ith the SM prediction\, intensifying the conflict that may arise in models
addressing the CKM unitarity violation.
One vector-like doublet
of quarks mixing with light quarks and the top quark can be the common or
igin of the CKM unitarity deficit or the tension in $V_{us}$ determinat
ions and the positive shift in $W$-boson mass\, without conflicting with
flavour-changing phenomena and electroweak observables.
Physarum polyceph
alum é um protista unicelular com numerosos núcleos cujo corpo é consti
tuído por uma rede de veias. À medida que explora o seu meio\, adapta-se
e otimiza a sua rede\, tendo em conta estímulos externos. Foi demonstrad
o que exibe comportamentos complexos\, como resolver labirintos\, encontra
r o caminho mais curto e criar redes robustas\, eficientes e económicas.
Vários modelos foram desenvolvidos para tentar simular a adapta
ção da sua rede para compreender os mecanismos por detrás do seu compor
tamento e desenvolver redes eficientes. Esta tese pretende estudar um mode
lo recentemente desenvolvido e fisicamente consistente baseado em fluxos d
e Hagen-Poiseuille adaptativos\; para tal\, irá determinar propriedades d
as árvores produzidas pelo modelo e irá examiná-las para determinar se
são realistas e consistentes com a experiência.
Esta tese tamb
ém pretende usar o mesmo modelo para produzir redes curtas e eficientes\,
aplicando-o a uma rede de transporte real. Observámos que o modelo é ca
paz de criar redes que são consistentes com outras redes biológicas: seg
uem a lei de Murray no estado estacionário\, mostram estruturas semelhant
es às presentes nas redes do Physarum e ainda exibem peristalse (oscilaç
ão dos raios das veias) e shuttle streaming (o movimento de trás para a
frente do citoplasma do Physarum) em algumas partes das redes.
Us
ámos também o modelo em conjunto com diferentes algoritmos estocásticos
para produzir redes curtas e eficientes\; quando comparadas com a rede fe
rroviária de Portugal continental\, todos os algoritmos produziram redes
mais eficientes que a rede real e alguns produziram redes com melhor rela
ção custo-benefício.
ABSTRACT:
The Teukolsky master equations describe the gauge inva
riant degrees of freedom in linear gravitational perturbations of the Kerr
black hole family. In this talk\, we focus on separable solutions to the
Teukolsky equations\, for which superradiance and trapping phenomena can b
e understood. Particular emphasis will be given to mode stability\, that i
s non-existence of exponentially growing or bounded but non-decaying separ
able solutions.
A corollary of our analysis is that general solu
tions to the Teukolsky equations are bounded and decay in time\; this is a
key first step in establishing (linear) stability of Kerr black holes. Th
is talk contains joint work with Marc Casals (Leipzig/CBPF/UC Dublin) and
Yakov Shlapentokh-Rothman (Toronto)
Jatos hadrónicos
surgem da fragmentação de quarks ou gluões altamente energéticos produ
zidos em aceleradores de partículas. Em colisões de iões pesados\, a in
teração de núcleos origina um estado de matéria nuclear conhecido como
Plasma de Quarks e Glúons (QGP). Ao atravessar este meio\, os jatos sofr
em perdas energéticas devido às interações com o QGP\, resultando na s
upressão e modificação dos jatos em relação às colisões de protão-
protão.
Ao estudar observáveis dos jatos\, as propriedades e d
inâmica do QGP são percebidas. Dentro deste contexto\, esta análise ava
lia os observáveis por meio de simulações baseadas em JEWEL\, um gerado
r de eventos Monte Carlo que inclui efeitos de supressão de jatos. Para a
primorar a compreensão dos mecanismos de perda de energia dos jatos\, est
e estudo examina o papel das partículas dispersas no meio\, juntamente co
m um análise em quantis para mitigar os efeitos de migração de bins e p
ermitir uma quantificação direta da energia média perdida pelos jatos.<
br/>
Além disso\, a dependência da perda de energia dos jatos com o
comprimento do meio atravessado será explorada considerando vários aspe
ctos geométricos da colisão\, especificamente a influência da forma do
meio e os efeitos de meios menos densos.
Teorias de gauge
representam algumas das forças fundamentais do Universo\, mas também mod
elos efetivos de Matéria Condensada a baixa energia. Enquanto para acopla
mento fraco as teorias de gauge admitem uma formulação continua\, para a
coplamento forte apenas estudos na rede são viáveis. Recentemente\, most
rou-se que teorias de gauge de ordem superior têm excitações geometrica
mente restritas - fases fractónicas.
Nós estudamos o diagrama
de fases de uma delas- a Hollow Rank-2 U(1) com matéria bosónica - na re
de\, com previsões numéricas de Monte Carlo. Foram obtidas previsões an
alíticas para gauge pura (sem matéria)\, onde as excitações de carga s
ão quadrupolares. Para acoplamento forte\, obtivemos uma lei de volume co
ncomitante com uma Fase de Confinamento Forte\, onde o potencial quadrupol
ar cresce quadraticamente com a separação entre cargas.
Para a
coplamento fraco\, encontramos a Fase de Confinamento Eletrostático com u
ma lei de área e potencial quadrupolar linear. Também estudamos a inclus
ão de campos de matéria Higgs bosónica com carga p=1. Os resultados ind
icam que as Fases de Confinamento Forte e Confinamento Eletrostático este
ndem-se para acoplamento fraco com matéria. Quando os campos de matéria
e gauge estão fortemente acoplados\, uma fase distinta surge.
D
enominada Fase Higgs\, em analogia com U(1) de ordem-1. Para um acoplament
o infinito com matéria\, apenas a Fase de Confinamento Forte sobrevive. N
o acoplamento infinito de gauge\, a teoria reduz-se ao modelo XY-plaquete
(3+1)D. Apresentamos o primeiro diagrama de fases completo para um modelo
fractónico com matéria bosónica\, ampliando o conhecimento sobre esses
candidatos a memória quântica tolerante a falhas.
Nesta tese é feito um resumo teórico focado no coração e na sua eletrofisiologia\, nomead amente na onda P do eletrocardiograma de superfície\, seguido de um estud o prospetivo acerca da possibilidade do uso de redes neuronais em R na pre visão de recorrência em pacientes com fibrilhação auricular sujeitos a uma ou mais ablações. A previsão é baseada quer em parâmetros eletro cardiográficos\, principalmente da onda P como validação de conceito\, quer em valores clínicos como o sexo e a idade. Os canais II\, V1 e aVF d o ECG\, canais onde a onda P é mais acentuada\, foram usados na extraçã o dos primeiros parâmetros\, inseridos posteriormente na rede neuronal. O modelo desenvolvido utiliza pacientes com arritmia e tem o potencial de i dentificar recorrência\, ainda que o número de casos utilizados para tre ino e teste da rede neuronal seja reduzido. Este método não é ainda uti lizado na prática clínica.
Com o aumento da base de dados utilizada nas fases de treino e teste\, é possível aument ar a eficácia do modelo.
END:VEVENT BEGIN:VEVENT SUMMARY:Digital Twin of the Electricity Generation and Demand in Portugal DTSTART:20230704T110000Z DTEND:20230704T130000Z DTSTAMP:20240329T082742Z UID:1a43c5fe-530e-431f-9873-15c1e1390ca4 SEQUENCE:1 CREATED:20230703T085241Z DESCRIPTION: Há várias metas energéticas a cumprir nas próximas décad as. Grande parte delas não será atingida se não compreendermos melhor c omo gastamos energia. O propósito da minha tese é expandir essa compreen são no cenário português\, criando um digital twin do consumo elétrico municipal\, mais precisamente\, um modelo horário que descreva o consumo de diferentes setores de atividade em todos os municípios de Portugal. I sto é obtido ao expandir consumo setorial anual usando perfis horários r elativos a cada setor.Os resultados foram validados com recurso a dois con juntos de dados distintos\, um possuindo consumo horário nacional\, e o o utro consistindo em consumo mensal municipal. Uma simples aplicação do m odelo foi testada\, nomeadamente a previsão do consumo elétrico de 2022. Isto foi feito prevendo o consumo anual de 2022 por município e setor\, e depois expandindo com recurso ao modelo\, sendo a validação feita da m esma forma.No final\, os resultados do modelo e da aplicação mostraram s e positivos\, com um erro inferior a 15% em 91% dos municípios do modelo\ , e em 89% dos municípios na aplicação\, estando o modelo pronto para s er integrado em ferramentas de planeamento energético a nível municipal/ nacional. LAST-MODIFIED:20230703T085241Z LOCATION:Sala C10\, Pavilhão Central\, Piso 1 URL:http://df.vps.tecnico.ulisboa.pt/eventos/digital-twin-of-the-electrici ty-generation-and-demand-in-portugal/ X-ALT-DESC;FMTTYPE=text/html: Há várias metas
energéticas a cumprir nas próximas décadas. Grande parte delas não ser
á atingida se não compreendermos melhor como gastamos energia. O propós
ito da minha tese é expandir essa compreensão no cenário português\, c
riando um digital twin do consumo elétrico municipal\, mais precisamente\
, um modelo horário que descreva o consumo de diferentes setores de ativi
dade em todos os municípios de Portugal. Isto é obtido ao expandir consu
mo setorial anual usando perfis horários relativos a cada setor.
Os resultados foram validados com recurso a dois
conjuntos de dados distintos\, um possuindo consumo horário nacional\, e
o outro consistindo em consumo mensal municipal. Uma simples aplicação
do modelo foi testada\, nomeadamente a previsão do consumo elétrico de 2
022. Isto foi feito prevendo o consumo anual de 2022 por município e seto
r\, e depois expandindo com recurso ao modelo\, sendo a validação feita
da mesma forma.
No final\, os resultados do modelo e da aplicação mostraram se positivos\, com um erro inferior a 15% em 91% dos municípios do modelo\, e em 89% dos municípios na aplic ação\, estando o modelo pronto para ser integrado em ferramentas de plan eamento energético a nível municipal/nacional.
END:VEVENT BEGIN:VEVENT SUMMARY:The diffusion of information in social media – How much complexi ty do we need? DTSTART:20230704T120000Z DTEND:20230704T140000Z DTSTAMP:20240329T082742Z UID:17127ff2-66d9-44cc-a93f-7fef0289667c SEQUENCE:1 CREATED:20230703T081611Z DESCRIPTION:Com o advento da era das redes sociais\, a quantidade de conte údo disponível aumentou radicalmente. A informação tem de competir pel o nosso tempo e nós escolhemos o que preferimos - a difusão da informaç ão é\, portanto\, ditada pela economia da atenção. Como resultado\, en quanto que alguns pedaços de informação são amplamente partilhados\, a maioria deles não é partilhado de todo. A causa desta distribuição é frequentemente atribuída ao fenómeno de Preferential Attachment (ligaç ão preferencial)\, no qual cada novo vértice adicionado à rede tem uma probabilidade maior de estabelecer uma ligação com um vértice já bem l igado. O resultado final é uma distribuição do tipo Power Law: alguns v értices têm muitas ligações\, mas a maioria deles tem um valor muito b aixo. A distribuição observada dos tamanhos de cascata pode surgir desta estrutura subjacente da rede. No entanto\, a popularidade de um determina do pedaço de informação também pode desempenhar um papel importante. C hamamos a esta característica\, "\;fitness"\;. Com o nosso trabal ho\, pretendemos determinar o que descreve melhor a difusão de informaç ão: se o fitness\, a rede ou uma combinação de ambos. Para o fazermos\, vamos usar dados do Twitter\, uma rede social. O Twitter permite estudar o problema de um modo quantitativo\, essencial para o estudo da difusão d e informação no mundo real. LAST-MODIFIED:20230703T081611Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/the-diffusion-of-information- in-social-media-how-much-complexity-do-we-need/ X-ALT-DESC;FMTTYPE=text/html:Com o advento da er
a das redes sociais\, a quantidade de conteúdo disponível aumentou radic
almente. A informação tem de competir pelo nosso tempo e nós escolhemos
o que preferimos - a difusão da informação é\, portanto\, ditada pela
economia da atenção. Como resultado\, enquanto que alguns pedaços de i
nformação são amplamente partilhados\, a maioria deles não é partilha
do de todo.
A causa desta distribuição é frequentemente atrib
uída ao fenómeno de Preferential Attachment (ligação preferencial)\, n
o qual cada novo vértice adicionado à rede tem uma probabilidade maior d
e estabelecer uma ligação com um vértice já bem ligado. O resultado fi
nal é uma distribuição do tipo Power Law: alguns vértices têm muitas
ligações\, mas a maioria deles tem um valor muito baixo. A distribuiçã
o observada dos tamanhos de cascata pode surgir desta estrutura subjacente
da rede.
No entanto\, a popularidade de um determinado pedaço
de informação também pode desempenhar um papel importante. Chamamos a e
sta característica\, "\;fitness"\;. Com o nosso trabalho\, preten
demos determinar o que descreve melhor a difusão de informação: se o fi
tness\, a rede ou uma combinação de ambos. Para o fazermos\, vamos usar
dados do Twitter\, uma rede social. O Twitter permite estudar o problema d
e um modo quantitativo\, essencial para o estudo da difusão de informaç
ão no mundo real.
Compreender as con
dições que permitem a emergência\, evolução e manutenção de coopera
ção é um problema teórico com importância actual. Por exemplo\, a sua
resolução poderia ajudar a resolver problemas de acção colectiva\, ou
seja\, problemas onde as actuais instituições sucumbem à Tragédia dos
Comuns.
Os efeitos de Sanções e Recompensas já foram analisa
dos como uma ferramenta efectiva para evitar a Tragédia dos Comuns e este
trabalho pretende analisar uma nova tipologia institucional que combina r
ecompensas e sanções juntamente com um mecanismo eleitoral\, no âmbito
da Teoria de Jogos Evolutiva.
Em particular\, propomos um modelo
onde indivíduos que fazem parte de uma determinada população participe
m num jogo N-pessoas com quatro estratégias à sua disposição: cooperar
\, desertar\, punir ou recompensar. Concluímos que esta tipologia é mais
eficaz que as alternativas mais simples a promover cooperação
ABSTRACT: < /p>
Terminal velocity reached by bubble walls in
first order phase transitions is an important parameter determining both p
rimordial gravitational-wave spectrum and production of baryon asymmetry i
n models of electroweak baryogenesis. We developed a numerical code to stu
dy the real-time evolution of expanding bubbles and investigate how their
walls reach stationary states.
Our results agree with profiles o
btained within the so-called bag model with very good accuracy\, however\,
not all such solutions are stable and realised in dynamical systems. Depe
nding on the exact shape of the potential there is always a range of wall
velocities where no steady state solutions exist. This behaviour in deflag
rations was explained by hydrodynamical obstruction where solutions that w
ould heat the plasma outside the wall above the critical temperature and c
ause local symmetry restoration are forbidden.
For even more aff
ected hybrid solutions causes are less straight forward\, however\, we pro
vide a simple numerical fit allowing one to verify if a solution with a gi
ven velocity is allowed simply by computing the ratio of the nucleation te
mperature to the critical one for the potential in question.
Abstract:
Dark matter direct searches place very stringent constraints on the poss
ible DM candidates proposed in extensions of the Standard Model. There are
however models where these constraints are avoided.
One of the
simplest and most striking examples comes from a straightforward Higgs por
tal pseudoscalar DM model with a softly broken U(1) symmetry. In this mode
l the tree-level DM-nucleon scattering cross section vanishes in the limit
of zero momentum-transfer. Furthermore\, adding doublets while keeping th
e pseudoscalar with the softly broken U(1) symmetry leads to the same resu
lt.
We have calculated the exact cross section at the one-loop l
evel in two of these scenarios\, which is several orders of magnitude larg
er than the tree-level one. I will also compare these results with scalar
DM models where the cancellation at tree-level does not occur. Finally I w
ill present results for a simple model with a vector dark matter particle.
Resumo
< p data-block-key="84dq4">Esta tese leva a cabo estudos no campo da termodi nâmica quântica\, propondo o conceito novo de Máquina de Campo Quântic o\, desenhada para executar tarefas específicas no domínio quântico. Pa ra descrever completamente o comportamento desta máquina\, são necessár ios conceitos de mecânica quântica e\, ao mesmo tempo\, ferramentas de f ísica estatística\, uma vez que não é viável descrever cada grau de l iberdade do sistema individualmente.Resumo:
< p data-block-key="5hrhk">Nesta tese\, é a presentada uma pesquisa para a produção de pares do parceiro supersimétrico mais leve do quark top\, o squark top (et 1 ). Esta pesquisa tem como alvo o decaimento em quatro pa rtículas do et 1 \, que é preferida quando a diferença de massa entre o squark top e a partícula supersimétrica mais leve é menor que a massa do bosão W.Abstract: < /p>
The problem of link prediction is to identify
missing or future connections in a complex network through the structural
patterns that emerge in their topology. A common approach uses path struc
tures between nodes\, quantifying direct and neighbouring node similaritie
s through a scoring function. Computing the scoring function for every pos
sible node combination can be computationally hard.
We design a
quantum link prediction algorithm based on continuous-time quantum walks (
CTQW)\, showing that is encodes a scoring function similar to classical pa
th-based link predictions methods. A CTQW is a simple model for quantum dy
namics and quantum computation on a graph. Finding applications of quantum
computing in complex networks can help speedup network science problems.
We further improve our algorithm and describe a sampling-based f
ramework for link prediction. We use a oracle-query access model to the in
put network and show that the complexity of implementing our quantum algor
ithm is limited by performing quantum simulation of the network’s adjace
ncy matrix. Considering the quantum simulation of d-sparse matrices\, wher
e d is the maximum number of entries in any row or column\, we show that t
here is a polynomial quantum speedup compared to classical sampling algori
thms for a fixed number of samples.
Despite this speedup\, the q
uantum simulation of d-sparse matrices is not efficient for complex networ
ks due to the existence of some nodes that are densely connected. As a fir
st step towards the efficient quantum simulation of complex networks\, we
show that a toy network model with mostly sparsely connected nodes and a f
ew densely connected ones can be efficiently simulated. Performing efficie
nt quantum simulation of complex networks could be an important routine fo
r quantum algorithms applied to network science problems in general.
<
br/> Furthermore\, in a different research direction\, we explore how quan
tum dynamics may be used for eneregy-efficient classical computation. We d
esign a 1-bit full adder operating with a quantum representation of classi
cal bits using electrons confined in quantum dots\, and discuss how the en
ergetic costs of computation could potentially be reduced. In our estimate
s we find that the energetic cost of cooling would be the main bottleneck
of this technology.
Abstract:
We consider the decay of a particle with some energy E_0 >\; 0 inside
the ergosphere of a black hole. After the first decay\, one of the particl
es with the energy E_1 <\; 0 falls toward the black hole\, while the sec
ond particle with E_2 >\; E_0 moves in the outward direction. The second
particle bounces back from a reflecting shell and the process repeats its
elf.
For radial motion of charged particles in the Reissner-Nord
ström black hole spacetime\, the result depends strongly on the concrete
scenario that one might consider. In particular\, an indefinitely large gr
owth of energy inside the shell is possible\, such that it gives rise to a
black hole bomb. We also consider a similar multiple process with neutral
particles in the background of a rotating axially symmetric stationary di
rty black hole.
We demonstrate that if particle decay occurs in
a turning point\, the black hole bomb in this case is impossible. For a ge
neric point inside the ergoregion\, there is a condition for the black hol
e bomb to exist. This condition relates the ratio of masses before and aft
er decay and the velocity of the fragments in the center of mass frame. We
also analyze a complementary case when the metric represents a naked sing
ularity and show that in this case a super-Penrose process is possible.
Abstract:I will present four models where light active neutrino masses are radia
tively generated. In the first one\, the tiny active neutrino masses are g
enerated via a three-loop radiative inverse seesaw mechanism\, with the Di
rac and Majorana submatrices arising at one-loop level. To the best of my
knowledge\, this is the first example of the inverse seesaw mechanism bein
g implemented with both submatrices generated at one-loop level.
The model is consistent with electroweak precision observables\, the elec
tron and muon anomalous magnetic moments as well as with the constraints a
rising from charged lepton flavor violation and the 95 GeV diphoton excess
. In the second model\, a dark sector seeds neutrino mass generation radia
tively within the linear seesaw mechanism and sizeable rates for charged l
epton flavor violation are obtained.
The third model is a Majoro
n-like extension of the Standard Model with an extra global U(1)X symmetry
where neutrino masses are generated through an inverse seesaw mechanism a
t the 1-loop level. The model is also consistent with charged lepton flavo
r violation and dark matter. The fourth one is a minimally extended inert
doublet model where the tiny neutrino masses are generated through a three
-loop seesaw. The model has viable dark matter candidates and leads to a r
ich phenomenology while satisfying all the current constraints imposed by
neutrinoless double-beta decay\, charged-lepton flavor violation\, and ele
ctroweak precision observables.
(Online)
Resumo
O processo de gera
ção de harmónicas de ordem superior (HHG) no estado sólido provocou um
a onda de interesse científico devido à perspetiva de criar novas fontes
compactas de radiação ultravioleta extrema (XUV) e de aproveitar a din
âmica ultra-rápida dos eletrões em sólidos. A possibilidade de criar m
ateriais com respostas ópticas personalizadas ou métodos de mapeamento d
a estrutura de bandas totalmente ópticas através de HHG continua a impul
sionar esta área de investigação.
Estudamos as interações d
e campo forte que caracterizam HHG em sólidos através de simulações ba
seadas na teoria do funcional da densidade dependente do tempo (TDDFT)\, c
om o objetivo de compreender os processos microscópicos por detrás da ge
ração da radiação harmónica.
Em particular\, modelamos MgO
e β-Ga2O3 em volume\, perturbados por impulsos laser de 40 fs no quase- e
médio-infravermelho (800 nm e 3 μm)\, e analisamos a dependência da in
tensidade das harmónicas na orientação relativa entre o cristal e os ei
xos de polarização. Adicionalmente\, estudamos os efeitos da alteração
da elipticidade do feixe nas harmónicos geradas em MgO. Fazemos uma comp
aração direta com um modelo intra-banda semi-clássico mais simples.
Modelamos com sucesso o comportamento dependente do tempo dos eletr
ões em sólidos e capturamos a transição dos regimes perturbativos para
não perturbativos a partir das simulações TDDFT. Os perfis de resposta
à polarização encontrados correspondem aos da experiência\, e concept
ualizamos um ponto de partida para o estudo de quantidades microscópicas
a partir de TDDFT em tempo real. A comparação dos resultados simulados c
om dados experimentais permitir-nos-á compreender e\, em última análise
\, controlar os mecanismos microscópicos da emissão harmónica em sólid
os.
Resumo:
O progresso rápido e recente da astronomia de o
ndas gravitacionais tornou necessário modelar fontes cada vez mais comple
xas. Durante a próxima década\, interferómetros de terceira geração e
a missão espacial LISA observarão binárias em centros galácticos envo
lvendo buracos negros supermassivos com milhões de massas solares.
O seu sinal diferá substancialmente das mais ``comuns'\;'\; b
inárias de buracos negros de igual massa que têm dominado as detecções
de ondas gravitacionais. Medições mais precisas de eventos mais extremo
s que excitam campos gravitacionais mais fortes podem ter um impacto treme
ndo em física fundamental\, astrofísica e cosmologia. Porém\, à escala
galáctica\, discos de acreção\, halos de matéria escura e densas popu
lações de objectos compactos podem interagir gravitacionalmente com corp
os em coalescência.
O papel que estas estruturas astrofísicas
desempenham na evolução e respectiva assinatura de ondas gravitacionais
de sistemas binários continua por explorar e estudos prévios dependeram
com frequência de aproximações Newtonianas ad-hoc. Nesta tese\, pretend
emos melhorar este panorama e responder a questões como: podem ambientes
de não-vácuo comprometer testes de Relatividade Geral e da natureza de b
uracos negros? Podemos colocar constrangimentos nas propriedades de ambien
tes astrofísicos com futuras observações de ondas gravitacionais? Em pa
rticular\, estudamos como deformações de maré de matéria presente à v
olta de buracos negros podem mascarar desvios a Relatividade Geral\, ou de
struir estruturas ``cabeludas'\;'\; que poderiam sinalizar a exist
ência de candidatos de matéria escura como campos bosónicos ultraleves.
Também exploramos a conexão profunda entre anéis de luz - ó
rbitas fechadas de partículas sem massa - e os modos próprios de oscila
ção de objectos compactos. Mostramos que\, independentemente da presenç
a de um ambiente\, o anel de luz controla como observadores distantes vêe
m matéria a cair num buraco negro\, ou como o buraco negro final formado
numa colisão relaxa para estacionariedade. Finalmente\, desenvolvemos o p
rimeiro framework completamente relativista capaz de estudar emissão de o
ndas gravitacionais em ambientes de não-vácuo.
Aplicamo-lo a b
inárias de buracos negros galácticas rodeadas por um halo de matéria es
cura e observamos a conversão entre ondas de matéria e ondas gravitacion
ais. Este acoplamento resulta em diferenças significativas no fluxo de en
ergia emitido\, que poderão ajudar a constrangir as propriedades de distr
ibuições galácticas de matéria. Os nossos métodos podem tornar-se a f
erramenta de referência para estudos de efeitos de ambiente em astronomia
de ondas gravitacionais e ser implementado em pipelines de análise de da
dos de colaborações futuras
Abstract:
Multi-Higgs-doublet models equipped with global symmetry groups\, either
exact or softly broken\, offer a rich framework for constructions beyond
the Standard Model and lead to remarkable phenomenological consequences. K
nowing all the symmetry options within each class of models can guide its
phenomenological exploration\, as confirmed by the vast literature on the
two- and three-Higgs-doublet models.
Here\, we begin a systemati
c study of finite non-Abelian symmetry groups which can be imposed on the
scalar sector of the four-Higgs-doublet model (4HDM) without leading to ac
cidental symmetries. In this work\, we derive the full list of such non-Ab
elian groups available in the 4HDM that can be constructed as extensions o
f cyclic groups by their automorphism groups.
This list is remar
kably restricted but it contains cases which have not been previously stud
ied. Since the methods we develop may prove useful for other classes of mo
dels\, we present them in a pedagogical manner.
ABSTRACT:
In recent years there has been an increased interest
in modelling the nonlinear dynamics in theories beyond general relativity.
Recent work by different groups has provided a new pathways towards perfo
rming numerical relativity simulations in such theories.
In this
talk\, I summarize subset of these ideas and will illustrate them in the
context of k-essence\, a subset of Horndeski theory. In particular\, I wil
l present and example where different extensions (or UV completions) of th
e theory allow for continuing the evolution past the Cauchy breakdown of t
he original theory.
Resumo:
Microfios de nitreto de gálio são estruturas muito int
eressantes devido às suas características intrínsecas e\, durante a úl
tima década\, diversos dispositivos optoelectrónicos baseados em microfi
os de GaN foram demonstados. Sendo um semicondutor com uma elevada resist
ência à radiação ionizante e estável à altas temperaturas\, os micro
fios de GaN também apresentam um potencial para serem aplicados como sens
ores de radiação em ambientes extremos. Os microfios têm uma altura at
é 30 µm e um diâmetro de 2 µm\, e devido a geometria e dimensão reduz
ida\, a sua estrutura cristalina é praticamente livre de deslocações.
Adicionalmente\, na sua configuração casca-núcleo apresenta um
a junçao p-n na direcção radial\, o que promove a detecção de carga.
Neste trabalho\, sensores de radiação baseados num único microfio foram
fabricados usando diversas técnicas de microfabricação e caracterizado
s por diferentes técnicas experimentais. Quando irradiados com protões c
om uma energia de 2 MeV\, a corrente eléctrica aumenta até quatro ordens
de grandeza relativamente à corrente escura com tempos de resposta infer
iores à 20 ms. Para além disto\, experiências de carga induzida por fei
xes de iões (IBIC) permitiram estudar a eficiência de colecção de carg
a (CCE).
Os resultados indicaram valores máximos na ordem dos 3
0%. Durante a irradiação\, verificou-se que até uma fluência de 1x1014
protões/cm2 a modificação das propriedades eléctricas dos sensores é
negligenciável. Para fluências mais elevadas a corrente começa a dimin
uir\, com uma queda mais abrupta entre 5x1014 protões/cm2 e 1x1015 protõ
es/cm2 .
No entanto\, mesmo após irradiar os dispositivos com u
ma fluência de 5x1015 protões/cm2 \, os sensores continuam a mostrar uma
resposta à radiação incidente. Tendo em conta as vantagens inerentes d
os microfios\, nomeadamente no que toca à possibilidade de detectar radia
ção ionizante e boa estabilidade\, verifica-se o seu potencial na aplica
ção em diversos campos onde se requer sensores com uma sólida resistên
cia à radiação ionizante.
Resumo:
< p data-block-key="b1bnu">Os algoritmos quânticos aproveitam leis da físi ca quântica para obter uma vantagem de complexidade comparativamente com estratégias clássicas de computação. Nesta tese\, apresentamos uma suc essão de trabalhos sobre algoritmos quânticos. Mostramos como acelerar m étodos computacionais clássicos com processadores quânticos\, desenvolv emos soluções quânticas para problemas de análise de dados\, generaliz amos uma técnica de simulação de passeios quânticos\, reinterpretamos uma interpolação algorítmica clássico-quântica e executamos simulaç ões em computadores quânticos reais.Um dos principais temas desta tese e acelerar métodos de reconstruç
ão de padrões com processadores quânticos. Desenvolvemos algoritmos qu
ânticos para recuperar padrões escondidos em dados com estrutura de graf
os. Estudamos o problema de tracking no contexto de experiências de físi
ca de partículas e demonstramos como acelerar um método comum de trackin
g com técnicas de amplificação de amplitude\; propomos uma versão quâ
ntica do algoritmo density peak clustering\; e desenvolvemos um algoritmo
quântico baseado em caminhos para previsão de ligações em redes comple
xas. Relacionado com o problema de previsão de ligações\, mostramos que
existe um eficiente algoritmo de simulação de passeios quânticos para
grafos que são esparsos a exceção de um número pequeno de hubs.
O outro tema e entender como obter speedups quânticos num futuro próx
imo\, enquanto os computadores quânticos continuarem extremamente vulner
áveis a ruído. Procuramos abordagens algorítmicas teóricas para reduzi
r as profundidades dos circuitos\, de forma a expor a computação a menos
ruído.
Analisamos um trade-off entre o speedup quântico e pro
fundidade do circuito para o problema de estimação de fase\, revelando q
ue este pode ser entendido no contexto do formalismo das transformações
quânticas de valores singulares. Também aplicamos uma ferramenta moderna
de super-resolução\, a “Minimização da Norma Atómica”\, a um pro
blema quântico de muitos corpos e mostramos que podemos reduzir significa
tivamente a profundidade dos circuitos envolvidos comparativamente com as
técnicas usuais de processamento de sinal.
Abstract:
Searches for new neutral Higgs bosons of an extended Higgs sector at the
LHC can be interpreted in the framework of the two-Higgs doublet model. B
y employing generic flavor-aligned Higgs?fermion Yukawa couplings\, we pro
pose an analysis that uses experimental data to determine whether flavor a
lignment is a consequence of a symmetry that is either exact or at most so
ftly broken. Our proposal is illustrated in two different scenarios based
on a few 3 sigma (local) excesses observed by the ATLAS and CMS Collaborat
ions in their searches for heavy scalars at Run 2 of the LHC.
Resumo
Os algoritmos de injeção de lasers normalmen
te usados em códigos de particle-in-cell (PIC) baseiam- se em sol
uções analíticas da equação de onda paraxial sob a aproximaça
̃o de envelope lento. Estes algoritmos são computacionalmente muito efi
cientes\, uma vez que dependem de soluções puramente analíticas. Ale
́m disso\, são ideais para descrever lasers em que o tamanho do foco e
a sua duração temporal são muito maiores que o comprimento de onda e
o período\, respetivamente. No entanto\, estes algoritmos falham ao des
crever a estrutura dos campos eletromagnéticos de pulsos de laser ultra
curtos (por exemplo\, de ciclo único) ou ultra focados\, os quais são
de elevada importância para a física a altas energias.
Usando esta nova injeção\, uma nova descrição teórica e numérica de acoplamentos espaço-tem porais em pacotes de ondas eletromagnéticos é desenvolvida\, permitind o a injeção de pulsos com velocidades focais arbitrárias\, conhecido s como pulsos flying focus. Este trabalho unifica duas descriçõ es existentes dessa classe de pacotes de ondas e inclui algumas simulaço ̃es iniciais de interação entre estes pulsos e plasmas de baixas dens idades.
END:VEVENT BEGIN:VEVENT SUMMARY:SEMANA DE ACOLHIMENTO DOS NOVOS ALUNOS DA LEFT DTSTART:20230907T140000Z DTEND:20230907T160000Z DTSTAMP:20240329T082742Z UID:ea8ccf70-e81a-44f2-ace6-da91a7565e6d SEQUENCE:1 CREATED:20230906T163735Z DESCRIPTION: LAST-MODIFIED:20230906T163735Z LOCATION:Pavilhão de Matemática\, Anfiteatro PA1\, piso -1 URL:http://df.vps.tecnico.ulisboa.pt/eventos/semana-de-acolhimento-dos-nov os-alunos-da-left/ END:VEVENT BEGIN:VEVENT SUMMARY:Results of Supernovae sample studies and its implications for theo retical modeling DTSTART:20230907T143000Z DTEND:20230907T160000Z DTSTAMP:20240329T082742Z UID:7319e331-9f11-4190-8a31-797b84ee7373 SEQUENCE:1 CREATED:20230901T082831Z DESCRIPTION: ABSTRACT: Supernovae (SNe) explosions mark the explosive deat h of a star. They are classified empirically based on their observed spect ral and light curve features. These features can be connected to the proge nitor star to derive pre-explosion characteristics. Some of the pre-explos ion characteristics are straight-forward (e.g: if there is hydrogen in the spectra\, the progenitor star should have retained its hydrogen layers du ring its whole evolution). Some are derived through theoretical models (e. g: if the spectra shows broad and boxy hydrogen lines without absorption c omponents\, it is possibly due to interaction of the SNe ejecta with a den se shell formed by circumstellar material accumulated during the explosion ). Theoretical models are not only useful to infer progenitor properties b ut also to predict what type of compact remnant will be produced by the ex plosion\, if any. Thus\, SNe characterization is of key importance to unde rstand both stellar evolution and the birth of compact objects. In this talk I will present the observational analysis done in samples of differen t types of SNe and the implications of the results for theoretical models. I will finish by presenting the possibilities and challenges that the new LSST survey presents for the field. LAST-MODIFIED:20230901T082831Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/results-of-supernovae-sample- studies-and-its-implications-for-theoretical-modeling/ X-ALT-DESC;FMTTYPE=text/html:ABSTRACT: < /p>
Supernovae (SNe) explosions mark the explosiv e death of a star. They are classified empirically based on their observed spectral and light curve features. These features can be connected to the progenitor star to derive pre-explosion characteristics. Some of the pre- explosion characteristics are straight-forward (e.g: if there is hydrogen in the spectra\, the progenitor star should have retained its hydrogen lay ers during its whole evolution). Some are derived through theoretical mode ls (e.g: if the spectra shows broad and boxy hydrogen lines without absorp tion components\, it is possibly due to interaction of the SNe ejecta with a dense shell formed by circumstellar material accumulated during the exp losion). Theoretical models are not only useful to infer progenitor proper ties but also to predict what type of compact remnant will be produced by the explosion\, if any. Thus\, SNe characterization is of key importance t o understand both stellar evolution and the birth of compact objects. In this talk I will present the observational analysis done in samples of di fferent types of SNe and the implications of the results for theoretical m odels. I will finish by presenting the possibilities and challenges that t he new LSST survey presents for the field.
END:VEVENT BEGIN:VEVENT SUMMARY:The role of ion channels in the transmissions of signals along axo ns DTSTART:20230912T100000Z DTEND:20230912T120000Z DTSTAMP:20240329T082742Z UID:9816a0df-50a2-49bb-b2fb-8c1d6899d2eb SEQUENCE:2 CREATED:20230908T211832Z DESCRIPTION:ResumoNeste trabalho\, propomos um modelo eletrofisiológico b idimensional que descreve a resposta dos neurónios ao serem estimulados e m condições de patch-clamp. Este modelo - uma versão reduzida do modelo de Hodgkin-Huxley - conserva as características essenciais da abordagem original\, sendo\, no entanto\, mais eficiente e informativo.Através da a nálise dos diagramas de bifurcação de diversos modelos reduzidos\, desc revemos as contribuições dos diferentes canais iónicos na estabilidade ou instabilidade da membrana neuronal. Para além disso\, exploramos a inf luência que a intensidade dos estímulos elétricos e vários parâmetros celulares têm na frequência de spiking dos neurónios.Também nesta tes e\, apresentamos um modelo do axónio que simula a transmissão unidirecio nal de sinais e que não é afetado por perturbações no potencial da mem brana. Após analisar o impacto da resistência intracelular e da capacit ância membranar na velocidade do sinal\, observamos discrepâncias consid eráveis entre os nossos resultados e os previstos pela equação de cabo (cable equation model).A nossa investigação revela também que\, quando a propagação do sinal ocorre sob a forma de múltiplos picos no potencia l da membrana do axónio\, há um transiente nos seus comprimentos de onda e frequências\, sendo esse transiente influenciado pela resistência int racelular. Consequentemente\, os picos têm velocidades distintas\, sendo o primeiro pico mais rápido que os restantes. Concluímos também que a v elocidade de propagação do primeiro pico - em alguns casos o único - se mantém relativamente constante ao longo do axónio\, independentemente d a intensidade do estímulo a que o neurónio está sujeito. O mesmo não s e observa em picos subsequentes. LAST-MODIFIED:20230908T211921Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/the-role-of-ion-channels-in-t he-transmissions-of-signals-along-axons/ X-ALT-DESC;FMTTYPE=text/html:Resumo
Neste trabalho\, propomos um modelo eletrofisioló
gico bidimensional que descreve a resposta dos neurónios ao serem estimul
ados em condições de patch-clamp. Este modelo - uma versão reduzida do
modelo de Hodgkin-Huxley - conserva as características essenciais da abor
dagem original\, sendo\, no entanto\, mais eficiente e informativo.
Através da análise dos diagramas de bif
urcação de diversos modelos reduzidos\, descrevemos as contribuições d
os diferentes canais iónicos na estabilidade ou instabilidade da membrana
neuronal. Para além disso\, exploramos a influência que a intensidade d
os estímulos elétricos e vários parâmetros celulares têm na frequênc
ia de spiking dos neurónios.
Tamb
ém nesta tese\, apresentamos um modelo do axónio que simula a transmiss
ão unidirecional de sinais e que não é afetado por perturbações no po
tencial da membrana. Após analisar o impacto da resistência intracelular
e da capacitância membranar na velocidade do sinal\, observamos discrep
âncias consideráveis entre os nossos resultados e os previstos pela equa
ção de cabo (cable equation model).
A nossa investigação revela também que\, quando a propagaçã o do sinal ocorre sob a forma de múltiplos picos no potencial da membrana do axónio\, há um transiente nos seus comprimentos de onda e frequênci as\, sendo esse transiente influenciado pela resistência intracelular. Co nsequentemente\, os picos têm velocidades distintas\, sendo o primeiro pi co mais rápido que os restantes. Concluímos também que a velocidade de propagação do primeiro pico - em alguns casos o único - se mantém rela tivamente constante ao longo do axónio\, independentemente da intensidade do estímulo a que o neurónio está sujeito. O mesmo não se observa em picos subsequentes.
END:VEVENT BEGIN:VEVENT SUMMARY:Simulating Gauge Theories: Bridging the Gap Between Classical and Quantum Simulations DTSTART:20230913T143000Z DTEND:20230913T160000Z DTSTAMP:20240329T082742Z UID:27ed4a5d-3b1e-4bde-8245-17868ea0553f SEQUENCE:2 CREATED:20230906T165441Z DESCRIPTION:Abstract:Quantum field theories at strong coupling\, as in Qua ntum Chromodynamics (QCD)\,require a non-perturbative approach. Lattice di scretizations and simulations providesuch an approach\, which has achieved remarkable success. This is the case\, forexample\, of QCD at zero chemic al potential. However\, in cases like at finite chemicalpotential or under real-time evolution\, the best techniques are still hindered by theso-cal led sign problems.The emergence of quantum simulators for gauge theories\, which aim to simulate these theories directly on quantum devices\, opens u p apromising new avenue for tackling these challenges. Rather than elimina ting the needfor classical computational approaches\, the latter becomes c rucial for validatingquantum simulators and as probes of quantum supremacy . This talk will delve intoboth classical and quantum approaches to tackli ng these problems. In particular\, wewill discuss the basic requirements n eeded for quantum simulating gauge theories\,how they call for new classic al approaches\, and how all of these open the door to theexploration of ne w physics. By bridging the gap between classical and quantumapproaches\, w e aim to advance our understanding of physics at a fundamental leveland pa ve the way for future advancements in simulating gauge theories. LAST-MODIFIED:20230906T165511Z LOCATION:Physics Seminar Room - Physics Building - 2nd floor (2-8.3) URL:http://df.vps.tecnico.ulisboa.pt/eventos/simulating-gauge-theories--br idging-the-gap-between-classical-and--quantum-simulations/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
Quant
um field theories at strong coupling\, as in Quantum Chromodynamics (QCD)\
,require a non-perturbative approach. Lattice discretizations and simulati
ons providesuch an approach\, which has achieved remarkable success. This
is the case\, forexample\, of QCD at zero chemical potential. However\, in
cases like at finite chemicalpotential or under real-time evolution\, the
best techniques are still hindered by theso-called sign problems.
The emergence of quantum simulators for gauge t
heories\,which aim to simulate these theories directly on quantum devices\
, opens up apromising new avenue for tackling these challenges. Rather tha
n eliminating the needfor classical computational approaches\, the latter
becomes crucial for validatingquantum simulators and as probes of quantum
supremacy.
This talk will delve intoboth classical and quantum a
pproaches to tackling these problems. In particular\, wewill discuss the b
asic requirements needed for quantum simulating gauge theories\,how they c
all for new classical approaches\, and how all of these open the door to t
heexploration of new physics. By bridging the gap between classical and qu
antumapproaches\, we aim to advance our understanding of physics at a fund
amental leveland pave the way for future advancements in simulating gauge
theories.
Abstract:
The
field of gravitational wave astronomy is allowing us to study the nature o
f compact objects in binary systems through their gravitational wave emiss
ion. Namely\, the tidal deformability of such objects\, encoded in their t
idal Love numbers (TLNs) gives us a window into their composition and th
e physics behind them.
However\, the increasing accuracy of futu
re gravitational wave detectors will likewise require a more accurate mode
ling of the emitted waveforms\, and therefore a more detailed study of TLN
s. In my talk\, I will present recent advances on how the spin of a compac
t object affects its TLNs. I will also discuss the impact these spin-tidal
effects will have on future gravitational wave detections\, focusing on n
eutron star binaries\, as well as other (dynamical) tidal effects and thei
r possible relevance in the near future.
Os lasers de alta p
otência e impulsos ultra-curtos na região do infravermelho médio (IR-m
édio\, ~3—8 μm) têm atraído crescente interesse da comunidade laser
na última década\, devido às suas aplicações em importantes áreas co
mo física de campo intenso. Em comparação com sistemas ultra-curtos com
dimensões na escala de metros no IR-próximo\, os lasers de IR-médio t
êm um potencial maior para gerar harmónicas mais altas\, suportando dura
ções extremamente curtas na ordem de poucos attossegundos\, devido à ex
tensão da energia de corte com o comprimento de onda do laser instigador
do processo. Um esforço significativo tem sido colocado no desenvolviment
o e refinamento desta tecnologia\, levando a vários avanços científicos
.
No entanto\, o dimensionamento destes sistemas para atingir en
ergias no nível do mJ é ainda um desafio elevado devido à quantidade li
mitada de materiais transparentes e dispositivos no IR-médio\, normalment
e caracterizados por limiares de dano mais baixos e perdas mais altas. A e
scassez de lasers ultra-curtos de estado sólido no domínio espectral de
IR-médio limitam a geração de impulsos energéticos a técnicas não-li
neares\, como a Amplificação Paramétrica Óptica de Impulsos Chirpados
(OPCPA). Estes métodos permitem não só a capacidade fundamental de ampl
ificação de banda larga\, mas também permitem uma ampla sintonização
de banda\, o que os torna ainda mais atrativos.
Nesta tese\, inv
estigamos e avaliamos a estratégia ideal para atingir impulsos de poucos
ciclos na ordem do mJ no infravermelho médio\, apresentando o trabalho re
alizado com três sistemas diferentes motivados pela sua capacidade em ger
ar impulsos próximos ou na região de infravermelho médio.
O t
rabalho descrito inclui: (i) optimização\, caracterização e compressã
o do sistema OPCPA já em operação com impulsos auxiliares próximos da
região do infravermelho médio. (ii) Estudos numéricos para geração de
impulsos ultra-curtos de alta energia no infravermelho médio usando cris
tais não lineares para OPCPA de banda ultra-larga. Avaliamos várias alte
rnativas para obter impulsos altamente energéticos de 3 μm com alto ganh
o e eficiência\, em estágios simples e múltiplos. (iii) Dimensionamento
de uma OPCPA no infravermelho médio para alcançar impulsos de poucos ci
clos e de multi-mJ através da extensão das capacidades do sistema de las
er no L2I/IST. Discutimos os passos para a implementação de um novo sist
ema de impulsos de 3 μm\, ultra-curtos (5 ciclos ópticos) e de alta ener
gia (5 mJ)\, e analisamos os principais desafios. (iv) Compressão de impu
lsos de alta energia na região do infravermelho médio.
Avaliam
os detalhadamente a compressão de diferentes impulsos no infravermelho m
édio gerados pelo sistema OPCPA nas instalações do AUO-ICFO. Potencial
para atingir impulsos tão curtos quanto 55 fs a 7 μm\, correspondendo a
2\,4 ciclos\, é demonstrado através da auto-compressão em materiais fin
os.
In this work\, we
propose a new treatment planning method for multi-beam FLASH radiotherapy
(Stitching FLASH) that combines FLASH delivered by proton beams\, with vo
lumetric modulated arc therapy (VMAT). The Stitching FLASH method requires
the target to be divided into different sections. For sections close to
an Organ-at-risk (OAR)\, proton FLASH beams were used to deliver radiatio
n dose. For the remaining target volume\, VMAT was used to achieve optimal
target coverage. To validate the Stitching FLASH method\, we used matRad
\, a treatment planning toolkit developed by DKFZ.
We applied i
t first\, as proof of concept\, to irradiate three spherical phantoms sur
rounded by several OARs and second\, to irradiate a cervical spinal cord
tumor\, which we then compared to the clinical VMAT plan. In our phantoms
study\, we managed to fulfil the minimum dose and dose-rate conditions fo
r protecting the OARs with FLASH\, while obtaining excellent target cover
age and superb dose conformity and homogeneity.
For the spinal c
ord tumor irradiation\, we were able to significantly increase the Clinic
al Target Volume (CTV) coverage and minimum dose\, while keeping the doses
in the OARs below the clinical thresholds using the FLASH protecting eff
ect. With the novel FLASH treatment planning method proposed in this work\
, we have demonstrated that it is possible to protect critical OARs\, whi
le maintaining excellent target coverage and dose homogeneity\, as well as
conformity. This shows that the Stitching FLASH method is promising for
proton FLASH radiotherapy
Resumo:
Os plasmas de fusão encontrados em reactores t
okamak são em grande extensão descritos com sucesso pelo modelo da Magne
to-hidrodinâmica (MHD). Este modelo prevê a existência de modos de Alfv
én discretos que são facilmente excitáveis através da interacção res
sonante com populações de iões energéticos. Esta interação pode leva
r ao crescimento exponencial dos modos e não só comprometer a operação
auto-sustentada dos reactores como também resultar em danos a alguns dos
seus componentes.
É\, portanto\, de extrema importância que s
e desenvolvam métodos para controlar estes modos durante a operação de
reactores de fusão. Nesta tese\, dois tipos de modos de Alfvén são estu
dados através de modelação numérica: as cascatas de Alfvén e os TAEs
(do inglês Toroidicity-induced Alfvén Eigenmodes). Os estudos foram cond
uzidos com dois objectivos principais: perceber a relação destes modos c
om parâmetros do equilíbrio tais como o perfil do factor de segurança\,
de forma a identificar detalhes do equilíbrio que podem ser inferidos at
ravés da observação dos modos em descargas (processo conhecido como esp
ectroscopia MHD)\; contribuir para o desenvolvimento de métodos para cont
rolar o aparecimento e crescimento destes modos.
Os estudos apre
sentados nesta tese contribuíram para a identificação numérica de dive
rsos tipos de cascatas observadas em descargas do Joint European Torus (JE
T). Em particular\, foram identificadas cascatas de alta frequência com p
adrões de frequência decrescente e\, pela primeira vez no JET\, cascatas
próximas do eixo magnético associadas a perfis monotónicos quase plano
s.
Adicionalmente\, a transição de modos cascata para TAEs foi
investigada\, de onde resultou a proposta de um método de espectroscopia
MHD para estimar a evolução do factor de segurança. É ainda apresenta
da nesta tese a análise de uma experiência dedicada à supressão de TAE
s utilizando a tecnologia de geração de corrente através da ressonânci
a ciclotrónica dos electrões (Electron Ciclotron Current Drive – ECCD)
. Estimativas dos efeitos de excitação e atenuação experienciados pelo
s modos indicam que a supressão dos modos está maioritariamente relacion
ada com o decréscimo da excitação por parte de uma população de part
ículas rápidas.
Abstract:One of the
spectacular successes of this millennium'\;s hadron spectroscopy expe
riments is the discovery of many exotic meson states in the heavy-quark en
ergy region\, which do not seem to fit into the conventional quark model p
icture. Our traditional understanding of hadrons is that they can be group
ed into mesons (quark-antiquark states) and baryons (which are made of thr
ee valence quarks). Moreover\, over the last years the LHCb collaboration
has found prominent peaks in the J/ψ-proton invariant mass spectrum. This
implies a minimal quark content uudc-cbar and thus constitutes the first
clear experimental evidence for pentaquarks. The proximity of those peaks
to meson-baryon thresholds suggests a molecular explanation in terms of me
son-baryon molecules\, in analogy to several exotic meson candidates in th
e charmonium sector.
The goal of th
is PhD project is to establish a theoretical description of pentaquarks fr
om a covariant five-body Bethe-Salpeter equation in QCD\, namely as five-b
ody systems made of four quarks and one antiquark where the (anti-)quarks
interact through gluons. This is based on a body of preceding work on meso
ns\, baryons and tetraquarks from 2-\, 3- and 4-body equations\, which hav
e been successful in describing the spectra and internal dynamics of these
states. Therefore\, the generalization of the approach to the five-body p
roblem will substantially advance the status quo and deliver predictions o
n the spectrum and structure of pentaquarks directly from QCD.
p>
In this seminar\, I will mainly focus on three works: I will present the technical basis for treating the five-body equa tion for a scalar system\, which provides the starting point for detailed studies in view of the resonance behavior of pentaquarks\, their internal structure\, and also light-quark spectroscopy to investigate meson-cloud e ffects on baryons. I will also present the ongoing work on the five-body e quation using the leading tensor components. Secondly\, I will present the two-body equation for a pentaquark as a meson-baryon system and describe how the Dyson-Schwinger and Bethe-Salpeter equations work. Finally\, I wil l briefly discuss another project I have been working on\, namely the QCD contributions to flavor changing neutral currents which may pose constrain ts on flavor anomalies.
END:VEVENT BEGIN:VEVENT SUMMARY:R&D: Radiation Hardness of Plastic Scintillating Materials for Sci ntillator Calorimeters DTSTART:20230927T100000Z DTEND:20230927T120000Z DTSTAMP:20240329T082742Z UID:85d37ab4-e18d-4739-8109-c6a965d1e962 SEQUENCE:3 CREATED:20230925T090014Z DESCRIPTION:In the quest to advance the field of high-energy physics\, fut ure experiments demand particle detectors that meet specific key factors o n the roadmap for their success. In the case of scintillator-based calorim eters or other detectors using scintillators\, the requirements are: high light yield\, fast signals\, dual readout capability\, high granularity\, and radiation hardness. These criteria provide the foundation for breakthr oughs in particle physics\, necessitating the exploration of innovative sc intillator materials. Currently\, one of the most cost-effective options f or particle detection is plastic scintillators. These materials possess th e unique property of producing scintillation\, detectable photons in the v isible part of the light spectrum\, upon interaction with ionizing radiati on or charged particles. Additionally\, they offer an exceptionally rapid light signal and a high light response. However\, scintillator plastics un dergo natural material degradation\, particularly in radiation-rich enviro nments. Hence\, identifying materials with enhanced radiation resistance i s crucial for advancing high-energy physics experiments. Polyethylene Naph thalate (PEN) and Polyethylene Terephthalate (PET) emerge as promising can didates for the development of new scintillator materials. Preliminary stu dies suggest that PET exhibits superior radiation resistance\, while PEN d emonstrates a higher light response compared to PET. Significantly\, both PEN and PET scintillate without the need for dopants. This context undersc ores the importance of investigating the feasibility of PEN/PET as fundame ntal materials for innovative scintillator plastics\, aligning seamlessly with the demands of future high-energy physics experiments. The primary ob jectives of this research project are develop cost efficient plastic scint illators with competitive characteristics to the existing ones\, in terms of light yield and transparency and develop competitive radiation hard sci ntillators This encompasses the development and characterization of new sc intillating plastics\, with initial focus on PEN and PET as well as charac terisation of commertial ones (for comparison). Furthermore\, we aim to as sess the materials'\; response to radiation exposure. Modeling the eff ects of various dose rates on the materials'\; radiation hardness will also be a significant aspect of our study. This research project is devel oped in collaboration with the Institute of Polymers and Composites (IPC) from the University of Minho\, who can produce plastic scintillators with different compositions. In this presentation\, we will show preliminary re sults regarding the production and characterization of these samples\, enc ompassing aspects such as light response\, emission spectra\, and transmit tance spectra. Additionally\, we will describe the irradiation planning fo r the samples and the simulation developed for comparing the light respons e between the samples and reference measurements. LAST-MODIFIED:20230927T085411Z LOCATION:Sala de Formação Avançada do DF (Sala 2-8.11 - 2º Piso do Pav ilhão de Física) URL:http://df.vps.tecnico.ulisboa.pt/eventos/rd-radiation-hardness-of-plas tic-scintillating-materials-for-scintillator-calorimeters/ X-ALT-DESC;FMTTYPE=text/html:In the quest to adv
ance the field of high-energy physics\, future experiments demand particle
detectors that meet specific key factors on the roadmap for their success
. In the case of scintillator-based calorimeters or other detectors using
scintillators\, the requirements are: high light yield\, fast signals\, du
al readout capability\, high granularity\, and radiation hardness. These c
riteria provide the foundation for breakthroughs in particle physics\, nec
essitating the exploration of innovative scintillator materials. Currently
\, one of the most cost-effective options for particle detection is plasti
c scintillators.
These materials possess the unique property of
producing scintillation\, detectable photons in the visible part of the li
ght spectrum\, upon interaction with ionizing radiation or charged particl
es. Additionally\, they offer an exceptionally rapid light signal and a hi
gh light response. However\, scintillator plastics undergo natural materia
l degradation\, particularly in radiation-rich environments. Hence\, ident
ifying materials with enhanced radiation resistance is crucial for advanci
ng high-energy physics experiments.
Polyethylene Naphthalate (PE
N) and Polyethylene Terephthalate (PET) emerge as promising candidates for
the development of new scintillator materials. Preliminary studies sugges
t that PET exhibits superior radiation resistance\, while PEN demonstrates
a higher light response compared to PET. Significantly\, both PEN and PET
scintillate without the need for dopants. This context underscores the im
portance of investigating the feasibility of PEN/PET as fundamental materi
als for innovative scintillator plastics\, aligning seamlessly with the de
mands of future high-energy physics experiments.
The primary obj
ectives of this research project are develop cost efficient plastic scinti
llators with competitive characteristics to the existing ones\, in terms o
f light yield and transparency and develop competitive radiation hard scin
tillators This encompasses the development and characterization of new sci
ntillating plastics\, with initial focus on PEN and PET as well as charact
erisation of commertial ones (for comparison). Furthermore\, we aim to ass
ess the materials'\; response to radiation exposure. Modeling the effe
cts of various dose rates on the materials'\; radiation hardness will
also be a significant aspect of our study.
This research project
is developed in collaboration with the Institute of Polymers and Composit
es (IPC) from the University of Minho\, who can produce plastic scintillat
ors with different compositions. In this presentation\, we will show preli
minary results regarding the production and characterization of these samp
les\, encompassing aspects such as light response\, emission spectra\, and
transmittance spectra. Additionally\, we will describe the irradiation pl
anning for the samples and the simulation developed for comparing the ligh
t response between the samples and reference measurements.
Abstract:
The p
rimary goal is the development of the instrumentation for an Orthogonal Pr
ompt-Gamma Imaging (OPGI) detector for range verification in Proton Therap
y treatments.
The experimental program includes tests with small
scale prototypes to assess the signal output and to develop preliminary in
strumentation to deal with a low number of channels. Crystals read by SiPM
devices were used to acquire waveforms for analysis.
Simultaneo
usly\, simulations were developed to study the performance of the system a
nd to study possible enhancements to the system\, namely the light collect
ion system. A solution for a large number of channels will be tested in th
e near future.
Abstract:
Phant
om Bethe excitations in integrable spin chains (XXZ\,XYZ Heisenbergmodel)
generate eigenstates with nontrivial topology\, a spin helix statebeing a
representative. I will show that it is natural to describe thesetopologica
l states with chiral basis instead of the computational basis. Wepropose a
n orthonormal basis for qubits\, and demonstrate its usage for anexperimen
tally relevant problem in cold atoms.
Abstract:Scattering theories are of large importance for many problems in Genera
l Relativity\, and scattering in the interior of a black hole is particula
rly relevant in the context of the cosmic censorship conjecture and the re
lated Cauchy horizon instability problem. The Cauchy horizon instability i
s thought to be directly linked to a notion of gravitational blue-shift at
the horizon\, which manifests itself as a blow-up in some observed quanti
ty.
By constructing the scattering channels\, one aims to recove
r information about the behavior of the field near the horizons\, where th
e instabilities might be seen as the unboundedness of the scattering opera
tors (energy blow-up) or from the lack of regularity at the horizon of the
propagating field (C^1-blow-up). In this talk I will present the recent d
evelopment of the scattering theories in the interior black holes between
the Cauchy horizon and the event horizon\, and the various blow-up results
.
From a mathematical point of view\, different fields exhibit c
ontrasting scattering phenomena. For example\, the scattering of linear wa
ves is delicate and surprising breakdowns of scattering happens in generic
situations.
Resumo:
Compreender a dinâmica fora do equilíbrio de
sistemas quânticos dissipativos\, onde a dissipação e a decoerência co
existem com a dinâmica unitária\, é um enorme desafio. Frequentemente\,
a única abordagem realista é renunciar a uma descrição microscópica
detalhada e\, ao invés\, procurar por assinaturas de comportamento univer
sal partilhadas por conjuntos de sistemas complexos distintos mas suficien
temente semelhantes. O caos quântico fornece o enquadramento estatístico
para abordar esta questão\, recorrendo a simetrias para obter informaç
ão não acessível de outra forma.
Esta tese examina como conci
liar caos com dissipação\, procedendo ao longo de duas linhas complement
ares. Na Parte I\, aplicamos a teoria das matrizes aleatórias não-Hermí
ticas a sistemas quânticos abertos com dissipação Markoviana e discutim
os as escalas de tempo de relaxação e estados estacionários de três ex
emplos representativos com crescente relevância física: Lindbladianos e
mapas de Kraus de uma partícula\, fermiões livres abertos e modelos de S
achdev-Ye-Kitaev (SYK) dissipativos. Para sistemas com caos quântico a um
corpo\, estabelecemos a universalidade dos seus estados estacionários. <
br/>
Para o modelo SYK com interações fortes\, descobrimos que o rel
axamento é dominado pela dissipação no regime de dissipação forte e d
ominado pelo caos\, com um hiato anormalmente grande\, no regime de dissip
ação fraca. Na Parte II\, investigamos as simetrias\, correlações e un
iversalidade de sistemas quânticos abertos de muitos corpos\, classifican
do vários modelos de matéria quântica dissipativa. Usamos o Hamiltonian
o SYK não-Hermítico como um modelo simplificado prototípico com não s
ó um estado estacionário ergódico universal mas também propriedades n
ão universais\, mas ainda genéricas\, de sistemas dissipativos quântico
s de muitos corpos na sua aproximação à ergodicidade.
Além d
isso\, vamos além dos Hamiltonianos não-Hermíticos efetivos e considera
mos a classificação de simetria dos Lindbladianos de muitos corpos. Enco
ntramos uma classificação com dez classes na ausência de simetrias unit
árias\, realizada em modelos realistas de cadeias de spin\, a qual pode s
er enriquecida por simetrias unitárias.
Em todos os exemplos\,
investigamos as correlações espectrais e confirmamos que elas são descr
itas pela teoria das matrizes aleatórias—o traço distintivo do comport
amento caótico quântico. Do ponto de vista teórico\, esta tese desenvol
ve um enquadramento genérico para o estudo das propriedades universais de
sistemas quânticos realistas\, caóticos e dissipativos. Do ponto de vis
ta prático\, fornece as componentes para a construção de evoluções di
nâmicas dissipativas restringidas por simetrias\, com potencial impacto t
ecnológico na fabricação de estruturas quânticas complexas
Abstract:
The
IceCube project at the South Pole melted 86 holes 2.5 kilometer deep in th
e Antarctic icecap to construct an enormous astronomical observatory. The
experiment discovered a flux of neutrinos from deep space with energies mo
re than a million times those of neutrinos produced at accelerator laborat
ories.
These cosmic neutrinos are created in some of the most vi
olent processes in the universe since the Big Bang and originate in the co
smic particle accelerators that are still enigmatic sources of cosmic rays
. This lecture will discuss the IceCube neutrino telescope and the discove
ry of high-energy neutrinos of cosmic origin.
It will highlight
the recent discovery that high-energy neutrinos—and cosmic rays—origin
ate in sources powered by rotating supermassive black holes.
Abstract: < /p>
We investigate dynamical properties of static
and spherically symmetric systems in the self-accelerating branch of the
Minimal Theory of Bigravity (MTBG). In the former part\, we study the gr
avitational collapse of pressure-less dust and find special solutions\, wh
ere\, in both the physical and fiducial sectors\, the exterior and interio
r spacetime geometries are given by the Schwarzschild spacetimes and the F
riedmann-Lemaitre-Robertson-Walker universes dominated by pressure-less du
st\, respectively\, with specific time slicings.
In the case tha
t the Lagrange multipliers are trivial and have no jump across the matter
interfaces in both the physical and fiducial sectors\, the junction condit
ions across them remain the same as those in general relativity (GR). For
simplicity\, we foliate the interior geometry by homogeneous and isotropic
spacetimes. We find interesting classes of exact solutions that represent
gravitational collapse in MTBG.
In the spatially-flat case\, un
der a certain tuning of the initial condition\, we find exact solutions of
matter collapse in which the two sectors evolve independently. In the spa
tially-closed case\, once the matter energy densities and the Schwarzschil
d radii are tuned between the two sectors\, we find exact solutions that c
orrespond to the Oppenheimer-Snyder model in GR. In the latter part\, we s
tudy odd-parity perturbations of the Schwarzschild-de Sitter solutions wri
tten in the spatially-flat coordinates.
For the higher-multipole
modes $\\ell\\geq2$\, we find that in general the system reduces to that
of four physical modes\, where two of them are dynamical and the remaining
two are shadowy\, i.e.\, satisfying only elliptic equations. In the case
that the ratio of the lapse functions between the physical and fiducial se
ctors are equal to a constant determined by the parameters of the theory\,
the two dynamical modes are decoupled from each other but sourced by one
of the shadowy modes.
Otherwise\, the two dynamical modes are cou
pled to each other and sourced by the two shadowy modes. At least for the
cases of collapse described in this paper\, we find that the ratio of the
lapse functions is determined by the properties of the collapse itself. On
giving appropriate boundary conditions to the shadowy modes as to not str
ongly back-react/influence the dynamics of the master variables\, in the h
igh frequency and short wavelength limits\, we show that the two dynamical
modes do not suffer from ghost or gradient instabilities.
The present resear
ch plan aims at understanding the interplay between incommensurability and
electronic interactions in systems with different dimensionalities\, incl
uding 1D quasiperiodic systems (QPS) and 2D moiré structures\, such as tw
isted bilayer graphene (tBLG).
Curr
ently\, there is not much overlap between the low-dimensional systems comm
unity and that dealing with incommensurability effects. In 1D QPS\, the ef
fects of incommensurability on localization and transport properties are w
ell established\, whereas they are almost completely neglected in most the
oretical studies related to 2D moiré systems. Conversely\, the study of m
oiré physics\, such as the formation of narrow-bands and the associated e
xotic correlation phenomena\, is overlooked in 1D QPS.
By studyi
ng the interplay between incommensurability and interactions\, we intend t
o bridge this gap and provide insights into the superconducting and correl
ated phases in tBLG. Our results will be of interest to other systems wher
e incommensurate structures can naturally appear or be induced\, such as o
ther twisted layered compounds and optical lattices.
Abstract
Development of thermoelectric (TE) materials is importa
nt\, for energy saving via waste heat power generation [1]\, and IoT power
sources [2]. For high TE performance\, tradeoffs must be overcome\, betwe
en Seebeck coefficient S and electrical conductivity s\, and between elect
rical and thermal conductivity k [3].
For the latter\, in additi
on to nanostructurings\, intrinsic low k mechanisms: Materials informatics
approach [4]\, doping leading to lattice softening [5]\, heterogeneous bo
nding from mixed anions [6]\, etc. For the first tradeoff\, magnetism can
be utilized to enhance S via magnon drag in CuFeS2 [7] and metastable Fe2V
Al-based thin films [8\,9]\, paramagnon drag in CuGaTe2 [10]\, Bi2Te3 [11]
etc.\, Spin fluctuation [12]\, Spin entropy [13].
Recently\, st
riking Cu doping effect in Mg3Sb2 : interstitial Cu doping lowered the pho
non group velocity\, while doping into the grain boundaries led to very hi
gh mobilities similar to single crystals\, while being low k polycrystalli
ne. An initial realistic 8-pair module exhibited efficiency of 7.3%@320oC\
, while estimated material efficiency ~11%! [14]. Tuning toward RT yielded
8-pair module with efficiency of 2.8%@100oC and cooling of 56.5 K [15]. R
ecently\, a single element device of doped Mg3Sb2 achieved efficiency ~12%
[16].
[1] L. E. Bell\, Science 321\, 1457 (2008)\, JOM\, 68\, 2673 (2016). [2] Sci. Tech. Adv. Mater. 19\, 836 (2018)\, MRS Bull.\, 43\, 176 (2018). [3] T. Mori\, Small 13\, 1702013 (2017)\, Energies\, 15\, 7307 (2022). [4] En ergy Environ. Sci.\, 14\, 3579 (2021). [5] Adv. Energy Mater.\, 11\, 21011 22 (2021). [6] J. Mater. Chem. A\, 9\, 22660 (2021)\, J. Mater. Chem. A\, 11\, 10213 (2023) Hot article. [7] Angew. Chem. Int. Ed. 54\, 12909 (2015) . [8] Phys. Rev. B\, 104\, 214421 (2021). [9] Nature 576 (7785) 85 (2019). [10] J. Mater. Chem. A\, 5\, 7545 (2017). [11] Mater. Today Phys.\, 9\, 1 00090 (2019). [12] Science Adv.\, 5\, eaat5935 (2019). [13] Sci. Tech. Adv . Mater.\, 22\, 583 (2021).[14] Joule\, 5\, 1196 (2021). [15] Nature Commu n.\, 13\, 1120 (2022). [16] Adv. Energy Mater.\, doi: 10.1002/aenm.2023016 6 Selected as Front Cover Article.
END:VEVENT BEGIN:VEVENT SUMMARY:Living with ghosts: stable edition DTSTART:20231019T143000Z DTEND:20231019T160000Z DTSTAMP:20240329T082742Z UID:51aefbfe-f517-448a-a36a-ad67a4d8e996 SEQUENCE:1 CREATED:20231013T130537Z DESCRIPTION:ABSTRACT: I will discuss our recent works Phys.Rev.Lett. 128 ( 2022) 4\, 041301 and ePrint: 2305.09631. There we presented a large class of mechanical models where a canonical degree of freedom interacts with an other one with a negative kinetic term\, i.e.\, with a ghost and yet the s ystem is totally stable. We proved analytically that the classical motion of the system is finite i.e. Lagrange stable for all initial conditions\, notwithstanding that the conserved Hamiltonian is unbounded from below and above. Moreover\, there are Lyapunov stable equilibrium configurations. N umerical computations fully supported this. Systems with negative kinetic terms often appear in modern cosmology\, quantum gravity\, and high energy physics and are usually deemed as unstable. Our result demonstrates that\ , for mechanical systems\, this common lore can be too naïve and that a s table living with ghosts is possible. LAST-MODIFIED:20231013T130537Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/living-with-ghosts-stable-edi tion/ X-ALT-DESC;FMTTYPE=text/html:ABSTRACT: I will di
scuss our recent works Phys.Rev.Lett. 128 (2022) 4\, 041301 and ePrint: 23
05.09631. There we presented a large class of mechanical models where a ca
nonical degree of freedom interacts with another one with a negative kinet
ic term\, i.e.\, with a ghost and yet the system is totally stable.
We proved analytically that the classical motion of the system is fini
te i.e. Lagrange stable for all initial conditions\, notwithstanding that
the conserved Hamiltonian is unbounded from below and above. Moreover\, th
ere are Lyapunov stable equilibrium configurations. Numerical computations
fully supported this.
Systems with negative kinetic terms often
appear in modern cosmology\, quantum gravity\, and high energy physics an
d are usually deemed as unstable. Our result demonstrates that\, for mecha
nical systems\, this common lore can be too naïve and that a stable livin
g with ghosts is possible.
Main aim: < /p>
To investigate the mechanisms triggering the
FLASH effect and the possibility of combination of FLASH and mini-beam tec
hniques in Cancer Therapy.
In recent years irradiations with ultra-hig
h dose rates (FLASH) have garnered attention due to the increased differen
tial response between normal tissue and cancer. The FLASH effect is charac
terized by the radioprotection of the healthy tissue while persevering the
clinical tumor control achieved by conventional radiotherapy\, but the me
chanisms that may lead to the flash effect FLASH are being investigated.In this work\, the properties of the chemical species generated through
the radiolysis of water are investigated as a possible surrogate of the F
LASH effect. The modeling perfomed will then be applied to the investigati
on of the combined application of FLASH and mini-beams to Cancer therapy.
Nesta tese\, são c
alculadas as constantes Newman-Penrose (NP) para um campo de spin-0 propag
ando no espaço-tempo de Minkowski\, com ênfase no comportamento próximo
ao infinito espacial e ao infinito nulo. Para alcançar isso\, é utiliza
da a estrutura do i^0 cilindro de Friedrich.
Sob a suposição d
e que os dados iniciais atendem a determinadas condições de regularidade
\, permitindo a extensão analítica do campo para conjuntos críticos\, o
estudo revela que as constantes NP no infinito nulo futuro I^ + e no infi
nito nulo passado I^ − são independentes uma da outra.
Noutra
s palavras\, as constantes NP clássicas em I ^± são determinadas por pa
rtes diferentes dos dados iniciais\, que são definidos em uma hipersuperf
ície de Cauchy. Por outro lado\, ao introduzir uma pequena generalizaçã
o conhecida como constantes NP do i^0 cilindro\, a necessidade da condiç
ão de regularidade é eliminada.
Estas constantes NP modificada
s fornecem quantidades conservadas em I^ ± que são exclusivamente determ
inadas por uma parte específica dos dados iniciais\, que\, por sua vez\,
correspondem aos termos que governam a regularidade do campo. Esta caracte
rística mostra-se fascinante no estudo de equações de evolução usando
a estrutura do i^0 cilindro.
Main aim:
Establish a new concept of radiation quality\, describing the radiation
by physical quantities that are related to the particle track structure at
the nanometre level. Characterisation of particle track structure is base
d on the frequency distribution of the size of ionisation clusters – Ion
isation Cluster Size Distribution - and associated parameters.
Abstract:
The
feasibility of using a Gd-based contrast agent as mean of in vivo dosimetr
y was explored up until now in the scope of the project. The characteristi
c x-ray peak of Gd (ca 43 keV) was studied under several scenarios to acce
ss the possibility of using it as a surrogate for in vivo and in real time
dose measurements. The dose and dose rate dependence of the Gd signal was
experimentally verified.
An increase of the Gd x-ray peak heigh
t was observed for increasing deposited doses at the target and a decrease
in the signal was measured for increasing dose rates. Several other varia
bles\, such as medium attenuation\, angle of detection and concentration o
f Gd in the tumor volume were researched in order to understand their impa
ct in the response of the dosimeter.
Finally\, the dosimeter was
tested in a scenario that aimed to simulate a treatment plan subjected to
uncertainties (in this case coming from movements of the target\, either
by inter-fraction displacement\, intra-fraction organ motion or overall ch
ange in the patient anatomy). A correlation between the x-ray Gd signal an
d the amount of irradiated volume was observed\, which makes it possible t
o track spatial changes in the deposition of dose.
For in depth displacements of the target\, a dependence with th
e energy of the incident particles was observed\, not being possible to ac
cess any correlation between Gd x-ray signal and total dose at the target.
The physics behind the secondary emission of the x-rays of inte
rest was also studied and it was seen that several processes are in the or
igin of the observed signal\, mainly particle induce x-ray emission and ne
utron capture events.
ABSTRACT: p>
A covariant\, gauge-invariant criterion for th
e existence\, or absence\, of gravitational radiation at infinity with non
-negative cosmological constant (Lambda) is presented. For Lambda>\;0\,
the fundamental idea is that the physical asymptotic properties are encode
d in {I\,h\,D}\, where I is a three-dimensional manifold\, h is a represen
tative of a conformal class of Riemannian metrics on I\, and D is a rank-2
\, traceless\, symmetric tensor field on I.
Based on this\, and
on the tidal nature of gravitational radiation\, a characterisation of gra
vitational radiation at the conformal boundary is given using the asymptot
ic properties of the rescaled Bel-Robinson tensor. The asymptotically flat
scenario is also reviewed. In this case\, the new criterion is shown to b
e fully equivalent to the classical one based on the news tensor. Also\, a
new balance law at infinity is presented. (Based on joint work with José
M. M. Senovilla)
Abstract:
We study dynamical solutions to the Einstein field equations (EFEs) in
the strong field regime of gravity\, making use of real or complex scalar
field matter which may induce gravitational collapse into black holes (BHs
). In that regime\, the nonlinearities of general relativity (GR) cannot b
e neglected and\, thus\, we employ numerical relativity (NR) simulations w
ith the aim to address various fundamental questions. In fact\, black hole
formation serves as an ideal laboratory in order to test the limits of th
e theory of general relativity and of our understanding of singularities.
On one hand\, by constructing a thought experiment\, the dynamic
al formation of astrophysical size black holes can facilitate the study of
a potential breakdown of the classical theory that may be associated to t
he creation of a singularity. On the other hand\, critical phenomena in gr
avitational collapse at the threshold between BH formation or dispersion p
robe naked singularities\, test the validity of the weak cosmic censorship
conjecture and\, consequently\, push the boundaries of our comprehension
of GR under extreme spacetime conditions. Our ultimate objective is to com
prehend the phenomena at the verge of collapse for diverse matter models\,
devoid of any symmetry assumptions.
Nevertheless\, there are se
veral intermediate stages that we must traverse to gradually progress towa
rds our ultimate goal. In this presentation\, I will focus on two primary
projects involving gravitational collapse that represent a direct outcome
of my Ph.D. research over the past two years.
The first project
explores the formation of astrophysical black holes through real scalar fi
eld collapse\, while the second project delves into the investigation of t
he threshold of collapse of a complex scalar field in axisymmetry. In the
forthcoming discussion\, we will explore the key findings\, implications\,
and future directions emerging from these projects\, providing valuable i
nsights into the active field of research of the threshold of gravitationa
l collapse and its consequences for our understanding of singularities in
GR.
Abstract:
The talk begins with an overview of the concept
ual problems of mechanics. Among these problems\, force and mass will be c
onsidered. Where they came from and how to overcome them are the questions
to be addressed in what follows.
Regarding the first\, the data
comes from the study of historical texts\, in particular the way physicis
ts articulated experiments and interpretations. We will see that Newton ne
ver wrote F=ma but force is interpreted according to Newton'\;s first
law of motion.
This articulation led to the most common definiti
on of force\, which has remained the same for more than two centuries. Reg
arding the question of how to overcome this problem\, an experiment that t
ests this concept will be presented. If it is possible to test concepts ex
perimentally\, we have a method for dealing with conceptual problems
<
/p>
END:VEVENT
BEGIN:VEVENT
SUMMARY:Towards hyperboloidal Numerical Relativity in Generalized Harmonic
Gauge
DTSTART:20231103T150000Z
DTEND:20231103T170000Z
DTSTAMP:20240329T082742Z
UID:4b026781-a3ec-4d76-a8a9-6eda1ee41b15
SEQUENCE:1
CREATED:20231103T092315Z
DESCRIPTION:Abstract: The use of hyperboloidal coordinates in the numerica
l evolution of hyperbolic Partial Differential Equations promise a clean c
apture of the radiation signal asymptotically. Although mathematically app
ealing\, a fully satisfactory application of such methods in Numerical Rel
ativity has not been achieved yet. One key difficulty is subtle interplay
between the decay of the evolved fields and divergent terms appearing from
the use of a compactified domain.In this talk I will present the numerica
l results of the recently understood asymptotic properties of the Generali
zed Harmonic Formulation of General Relativity for some choice of gauge an
d metric functions. In particular\, I will discuss 3+1-dimensional evoluti
on of a simplified model with the same asymptotics\, as well as full non-l
inear General Relativity evolutions under the assumption of spherical symm
etry. These works are steps towards applying hyperboloidal methods in full
Numerical Relativity without symmetry assumptions\, which could improve t
he Gravitational Wave extraction procedure significantly.
LAST-MODIFIED:20231103T092315Z
LOCATION:Sala de Formação Avançada do DF (Sala 2-8.11 - 2º Piso do Pav
ilhão de Física)
URL:http://df.vps.tecnico.ulisboa.pt/eventos/towards-hyperboloidal-numeric
al-relativity-in-generalized-harmonic-gauge/
X-ALT-DESC;FMTTYPE=text/html:
Abstract:
The use of hyperboloidal coordinates in the numerical
evolution of hyperbolic Partial Differential Equations promise a clean ca
pture of the radiation signal asymptotically. Although mathematically appe
aling\, a fully satisfactory application of such methods in Numerical Rela
tivity has not been achieved yet.
One key difficulty is subtle i
nterplay between the decay of the evolved fields and divergent terms appea
ring from the use of a compactified domain.
In this talk I will presen
t the numerical results of the recently understood asymptotic properties o
f the Generalized Harmonic Formulation of General Relativity for some choi
ce of gauge and metric functions.
In particular\, I will discuss
3+1-dimensional evolution of a simplified model with the same asymptotics
\, as well as full non-linear General Relativity evolutions under the assu
mption of spherical symmetry. These works are steps towards applying hyper
boloidal methods in full Numerical Relativity without symmetry assumptions
\, which could improve the Gravitational Wave extraction procedure signifi
cantly.
Resumo:
Soluções das equações de Einstein que estão
próximas do limite de formação de buracos negros exibem característic
as que relembram fenómenos críticos em mecânica estatística. Neste tra
balho\, estudamos detalhadamente o colapso crítico de um campo escalar\,
focando-nos tanto em aspetos locais como globais.
Primeiro\, mos
tramos que o campo que colapsa é discretamente auto-semelhante com um per
íodo de eco de Δ≈3.4. Notavelmente\, quantidades globais como a massa
de Bondi ou a função de notícias manifestam o mesmo comportamento discr
etamente auto-semelhante. Segundo\, demonstramos que a massa de buracos ne
gros formados em evoluções perto do limite escala em função da distân
cia ao parâmetro crítico\, com um expoente crítico de γ≈0.37. Por ú
ltimo\, argumentamos que estes resultados são universais em relação aos
dados iniciais.
O nosso esquema numérico é baseado numa formu
lação característica em coordenadas de Bondi compactificadas\, com mét
odos que são globalmente precisos à quarta ordem. A convergência do có
digo é testada e a precisão é melhorada empregando um refinamento anal
ítico da grelha. Finalmente\, o colapso de um campo de Yang-Mills é estu
dado. Este código mostra boa convergência e é fornecida uma análise pr
eliminar do seu colapso crítico.
O desenvolvimento d
a hélio- e asterossismologia revolucionou a astrofísica moderna reveland
o o interior previamente inacessível das estrelas\, fornecendo restriçõ
es novas e independentes ante as quais é possível testar a física estel
ar\, e revelando algumas discrepâncias na reconciliação entre a modela
ção do interior e da superfície das estrelas.
Neste trabalho explora-se a utilização de neutrinos como u
ma forma de sondar a composição e a estrutura estelar. Num primeiro caso
\, demonstra-se que o estado-da-arte da astronomia de neutrinos é suficie
nte para obter informações relativas à abundância de elementos-chave e
m regiões bem determinadas do Sol\, e num segundo\, mostra-se a existênc
ia de uma ligação entre neutrinos e asterossismologia durante o flash de
hélio que poderá ser usada para responder à questão em aberto sobre o
s processos físicos relacionados com este fenómeno.
É demonstrado que uma precisão de 17% na observação
do fluxo de neutrinos solares é suficiente para distinguir entre dois mo
delos de composição\, e são calculados os fluxos e os perfis radiais de
emissão destes neutrinos.
Adicion almente\, também se mostra que a observação direta do flash de hélio é possível para estrelas até cerca de 25 pc da Terra\, através da dete ção de neutrinos\, e que o fluxo específico de neutrinos provenientes d o decaimento de 18F podem limitar a abundância de 14N numa zona muito pre cisa da estrela. Finalmente\, demonstra-se o papel determinante dos neutri nos térmicos na estrutura do flash de hélio\, revelando uma ligação en tre a asterossismologia e a emissão de neutrinos.
END:VEVENT BEGIN:VEVENT SUMMARY:Monte Carlo Algorithms for Low-Temperature Plasmas DTSTART:20231109T100000Z DTEND:20231109T120000Z DTSTAMP:20240329T082742Z UID:a0baebca-04e6-4a5c-a271-f8098522374f SEQUENCE:1 CREATED:20231020T102811Z DESCRIPTION:Abstract The main aim of this thesis is to develop and employ Monte Carlo (MC) modelling techniques for the investigation and taming of low-temperature plasmas (LTPs). MC methods simulate physical systems by tr acking the temporal of evolution of test particles. The stochastic evoluti on is performed by generating random numbers sampled from distributions th at emulate the underlying physics. In Chapter 2\, we present a MC method f or solving the complex chemical kinetics of heavy species in LTPs. Additio nally\, novel variance reduction methods are developed to improve the desc ription of minority species without impacting computation time. In Chapter 3\, we present the first version of the LoKI-MC open-source code\, which addresses electron kinetics in a gas discharge subjected to a uniform DC e lectric field. In Chapter 4\, we expand the LoKI-MC capabilities to includ e anisotropic scattering in any collision type. Moreover\, we demonstrate that the inclusion of anisotropic scattering in rotational collisions with H2O molecules is fundamental to obtain accurate agreement between modelli ng and experiment. In Chapter 5\, we extend the formulation to configurati ons involving AC/DC electric and DC magnetic fields. The code is thoroughl y verified\, and novel benchmark calculations are produced. Additionally\, we analyze the impact of magnetic fields in detail\, distinguishing betwe en configurations with DC and AC electric fields. Finally\, in Chapter 6\, we consider the rigorous time-dependent MC solution as the gold standard to evaluate the accuracy of two common assumptions for solving space- and time- dependent electron kinetics: the local-field approximation (LFA) and the local-energy approximation (LEA). The study focuses on homogeneous el ectron kinetics in nanosecond-pulsed discharges. It is observed that the L EA generally provides more accurate results than the LFA. In general\, the methods presented in this thesis allowed for a better understanding of LT Ps and an assessment of the accuracy of common approximations used in LTP modelling. LAST-MODIFIED:20231020T102811Z LOCATION:Anfiteatro PA3 (Piso -1 do Pavilhão de Matemática) URL:http://df.vps.tecnico.ulisboa.pt/eventos/monte-carlo-algorithms-for-lo w-temperature-plasmas/ X-ALT-DESC;FMTTYPE=text/html:Abstract
The main aim of this thesis is to develop and e
mploy Monte Carlo (MC) modelling techniques for the investigation and tami
ng of low-temperature plasmas (LTPs). MC methods simulate physical systems
by tracking the temporal of evolution of test particles. The stochastic e
volution is performed by generating random numbers sampled from distributi
ons that emulate the underlying physics. In Chapter 2\, we present a MC me
thod for solving the complex chemical kinetics of heavy species in LTPs. A
dditionally\, novel variance reduction methods are developed to improve th
e description of minority species without impacting computation time.
In Chapter 3\, we present the first version of the LoKI-MC open-sour
ce code\, which addresses electron kinetics in a gas discharge subjected t
o a uniform DC electric field. In Chapter 4\, we expand the LoKI-MC capabi
lities to include anisotropic scattering in any collision type. Moreover\,
we demonstrate that the inclusion of anisotropic scattering in rotational
collisions with H2O molecules is fundamental to obtain accurate agreement
between modelling and experiment. In Chapter 5\, we extend the formulatio
n to configurations involving AC/DC electric and DC magnetic fields.
The code is thoroughly verified\, and novel benchmark calculations ar
e produced. Additionally\, we analyze the impact of magnetic fields in det
ail\, distinguishing between configurations with DC and AC electric fields
. Finally\, in Chapter 6\, we consider the rigorous time-dependent MC solu
tion as the gold standard to evaluate the accuracy of two common assumptio
ns for solving space- and time- dependent electron kinetics: the local-fie
ld approximation (LFA) and the local-energy approximation (LEA).
The study focuses on homogeneous electron kinetics in nanosecond-pulsed d
ischarges. It is observed that the LEA generally provides more accurate re
sults than the LFA. In general\, the methods presented in this thesis allo
wed for a better understanding of LTPs and an assessment of the accuracy o
f common approximations used in LTP modelling.
ABSTRACT:
The Gaia mission as well as large-scale ground-based
spectroscopic surveys are collecting complex data for millions (even bill
ions) of stars. The community is therefore using more and more machine-lea
rning methods to cope with the amount of data.
In this talk I wi
ll present some recent examples of supervised (typically regression) and u
nsupervised (typically dimensionality reduction and clustering) methods in
the context of stellar and Galactic astrophysics. In particular in the fi
eld of Galactic open clusters\, the combination of Gaia data with machine-
learning approaches is revolutionizing a whole field.
Resumo
Nesta tese\, estudamos a reação à radiação
eletromagnética de partículas carregadas em movimento circular em torno
de um buraco negro de Schwarzschild imerso num campo magnético assintotic
amente uniforme. Sem considerar radiação\, as órbitas circulares neste
sistema estão restritas ao plano equatorial e podem ser caracterizadas co
mo estando na configuração positiva ou negativa\, dependendo se a força
de Lorentz aponta para fora ou para dentro da trajetória\, respectivamen
te. Se incluirmos a radiação\, a equação de movimento é a equação d
e DeWitt-Brehme\, que inclui um termo de cauda complexo\; há resultados n
a literatura que afirmam que esse termo pode ser negligenciado.
<
/p>
Assim\, neste trabalho realizamos uma análise
do limite Newtoniano que mostra que a cauda não pode ser negligenciada n
esse limite\, a menos que toda a radiação seja ignorada\, ou a curvatura
em si seja negligenciável\, dois cenários triviais em que nunca se usar
ia a equação DeWitt-Brehme.
Tamb
ém estudamos a reação à radiação no regime de campo forte\, usando t
eoria de perturbações de buracos negros. Encontramos expressões para o
fluxo de energia no horizonte e no infinito em todos os modos multipolares
\, para raio orbital e velocidade angular genéricos. Em seguida\, calcula
mos os fluxos de energia propriamente ditos usando métodos analíticos (l
imitados a movimentos lentos e a modos de baixa frequência) e métodos nu
méricos\; os dois concordam dentro do domínio de validade dos resultados
analíticos. Para os valores da frequência do ciclotrão estudados\,
descobrimos que o fluxo de energia total pode ser calculado com precisão
arbitrária (excluindo erros numéricos) usando um número finito de modos
\; isso parece falhar para órbitas muito próximas ao horizonte de aconte
cimentos (existem órbitas estáveis nessa região para a configuração p
ositiva).
Descobrimos também que\, para órbitas na configuraç
ão positiva\, o aumento do raio orbital leva a que a razão entre o fluxo
de energia no horizonte e em infinito de aproxime do valor constante p
ara o modo dipolar\, enquanto que tende para infinito para os multipólos
de ordem superior. Finalmente\, em relação ao termo de cauda na equaçã
o de DeWitt-Brehme\, o caso de campo forte apenas reforça a afirmação a
nterior de que ele não pode ser negligenciado no estudo da reação de ra
diação na solução de Schwarzschild em qualquer cenário não trivial.<
/p>
END:VEVENT
BEGIN:VEVENT
SUMMARY:Energetics of quantum information processing
DTSTART:20231114T170000Z
DTEND:20231114T190000Z
DTSTAMP:20240329T082742Z
UID:6486ce7d-d938-4828-97d4-81f65453413d
SEQUENCE:1
CREATED:20231110T092729Z
DESCRIPTION: Abstract:I present the main projects of my doctoral thesis\,
whose aim is to understand the energy requirements and limitations of quan
tum information processing. First\, we demonstrate classical logic process
ing using a trapped-ion quantum computer. A three-bit half-adder is implem
ented using electronic states of trapped ions. We discuss the energetics b
y measuring consumed power and theoretical modeling. Second\, we investiga
te energy-fidelity trade-offs when implementing unitaries in driven quantu
m systems. The fidelity of the operation is quantified by tracing out the
degrees of freedom of the driving system\, and rigorous mathematical bound
s are sought for fidelity guarantees independent of the unitary operation.
Finally\, the implications of these mathematical bounds are explored in g
eneral quantum algorithms using the framework of Quantum Singular Value Tr
ansforms (QSVT)\, including the impact of error correction on error-energy
scaling.
LAST-MODIFIED:20231110T092729Z
LOCATION:Online
URL:http://df.vps.tecnico.ulisboa.pt/eventos/energetics-of-quantum-informa
tion-processing/
X-ALT-DESC;FMTTYPE=text/html:
Abstract:
I pr
esent the main projects of my doctoral thesis\, whose aim is to understand
the energy requirements and limitations of quantum information processing
. First\, we demonstrate classical logic processing using a trapped-ion qu
antum computer.
A three-bit half-adder is implemented using elec
tronic states of trapped ions. We discuss the energetics by measuring cons
umed power and theoretical modeling. Second\, we investigate energy-fideli
ty trade-offs when implementing unitaries in driven quantum systems. The f
idelity of the operation is quantified by tracing out the degrees of freed
om of the driving system\, and rigorous mathematical bounds are sought for
fidelity guarantees independent of the unitary operation.
Final
ly\, the implications of these mathematical bounds are explored in general
quantum algorithms using the framework of Quantum Singular Value Transfor
ms (QSVT)\, including the impact of error correction on error-energy scali
ng.
Abstract:
In 2023 we celebrate 30 years of the Lasers and Plasmas Group. In this c
olloquium\, I will discuss the first steps in this area at IST\, including
the origins of plasma physics and laser-plasma interaction studies\, the
first laser based on the Chirped Pulse Amplification technique (recognized
with the 2018 Nobel Prize) from the Iberian Peninsula and the launch of e
xperimental research in laser-plasma and beam-plasma interactions\, includ
ing harmonic generation and attosecond pulses\, and some of the scientif
ic and technological milestones of the last 30 years.
I will als
o present some of the scientific and technological frontiers associated wi
th the most powerful and intense lasers and particle beams that suggest th
at the next 30 years will also be filled with exciting scientific and tech
nological advances.
Resumo
< p data-block-key="5p20f">Bepicolombo é uma missão conjunta entre a Europ ean Space Agency (ESA)\, e a Japan Aerospace Exploration Agency (JAXA) par a explorar Mercúrio. É composta por duas naves\, a Mercury Planetary Orb iter (MPO) da ESA e a Mercury Magnetospheric Orbiter (MMO) da JAXA. A miss ão foi lançada em 2018 e está previsto entrar em orbita de Mercúrio em Dezembro de 2025.O advento da energi
a de fusão nuclear tem sido altamente antecipado há mais de um século.
Neste trabalho\, exploramos um conceito promissor para alcançá-la atrav
és do confinamento magnético\, o stellarator\, que quebra a simetria do
tokamak\, permitindo operação em estado estacionário. Desenvolvimentos
recentes no design de dispositivos de fusão por confinamento magnético p
ermitiram a construção de configurações de stellarators excepcionalmen
te otimizadas.
A otimização deste design exige o cálculo iter
ativo do equilíbrio magnético\, tendendo a ser computacionalmente dispen
diosa. Esta otimização pode ser acelerada recorrendo a uma aproximação
a um equilíbrio magnético\, obtida através de uma expansão em torno d
o eixo magnético. A expansão fornecida tem demonstrado possibilitar a co
nstrução de configurações magnéticas com boas propriedades de confina
mento\, ao mesmo tempo que requer apenas uma fração do tempo de cálculo
habitual para gerar equilíbrios magnéticos otimizados.
No ent
anto\, pouco se sabe sobre as características gerais das órbitas de part
ículas rápidas calculadas em tais equilíbrios analíticos\, embora simp
lificados\, em comparação com aquelas obtidas em soluções de equilíbr
io mais precisas Este trabalho tem como objetivo investigar e demonstrar o
potencial da expansão em torno do eixo para fornecer informações preci
sas sobre as órbitas de partículas e para calcular as frações de perda
em diferentes tipos de stellarator. As configurações usadas foram redim
ensionadas para parâmetros relevantes para a fusão e aproximam a quasisi
metria em vários graus.
Isso permite-nos entender como os desvi
os da quasisimetria podem afetar as órbitas das partículas e o seu efeit
o na estimativa da fração de perda de partículas para a parede. As traj
etórias do centro-guia das partículas alfa nascidas da fusão são traç
adas usando os códigos \\texttt{gyronimo} e \\texttt{SIMPLE} sob o enquad
ramento do código \\texttt{NEAT}\, mostrando boa concordância numérica
Discrepâncias entre equilíbrios precisos e os seus correspondentes na ex
pansão perto do eixo têm efeitos menores em partículas passantes\, mas
efeitos significativos em partículas presas\, especialmente em campos mag
néticos quasi-helicamente simétricos As frações de perda de partícula
s concordam no regime de perdas imediatas\, mas divergem posteriormente. <
br/>
As perdas de partículas até 1 ms parecem ser eficazmente modela
das pela expansão junto ao eixo para configurações quasi-axisimétricas
Expressões analíticas foram encontradas para estimar larguras de órbit
a e separatrizes de passagem-aprisionamento de partículas em campos quasi
simétricos.
ABSTRACT: p>
Modern observational cosmology suffers from wo
rrying unsolved puzzles (i.e.\, Hubble tension) that can point towards the
existence of unaccounted systematic biases in the observations\, particul
arly related to the calibration of standard candles in the local distance
ladder\, such as Cepheids and supernovae.
In the case of type Ia
supernovae (SNe Ia)\, this is further hinted at by the existence of a mas
s-step\, a well-documented discrepancy between the calibrated luminosities
of SNe Ia originating in low- and high-mass galaxies\, which might indica
te that different galaxy populations occur in different rungs of the dista
nce ladder.
In this talk\, I will discuss some attempts to impro
ve SN Ia calibration\, focusing mainly on a more detailed description of d
ust reddening. Furthermore\, I will explore to what extent host galaxy dus
t data can be leveraged to improve the SN calibration.
Os laboratórios co
ntrolados remotamente\, durante a pandemia COVID-19\, tiveram progressos s
ignificativos. Sendo o conceito deste tipo de laboratórios relativamente
antigo\, os mesmos até então tinham tido pouca visibilidade. O mundo aca
démico foi forçado a aumentar a oferta de experiências remotas com maio
r regularidade e mais fiáveis e consistentes\, devido a este estímulo ex
terno.
Desde 2000\, o Instituto Su
perior Técnico (IST) fornece várias experiências remotas no seu laborat
ório remoto e-lab. No entanto\, foi necessária a atualização de algum
hardware e software\, devido à evolução da tecnologia. Assim\, para col
matar esta necessidade\, foi desenvolvido o ”framework for remote experi
ments in education” (FREE).
Utili zando um computador ou um dispositivo móvel\, ligados a uma rede de Inter net pública\, é possível ter acesso ao laboratório e-lab através de u m browser sem necessidade de instalar qualquer software adicional. Os util izadores podem realizar inúmeras atividades experimentais e os resultados podem ser descarregados a partir da base de dados da aplicação. Com est es dados\, realizando a adequada análise dos mesmos podem-se obter os par âmetros físicos. Também são apresentadas as instruções de como integ rar uma nova experiência no FREE. A cavidade eletromagnética foi utiliza da como prova de conceito. Incluindo ainda exemplos de conjuntos de dados típicos\, que se podem obter\, e a análise necessária para determinar a densidade do plasma.
END:VEVENT BEGIN:VEVENT SUMMARY:Measurements of Higgs boson properties in associated production wi th top quarks with the ATLAS detector DTSTART:20231120T150000Z DTEND:20231120T170000Z DTSTAMP:20240329T082742Z UID:2a5d42a5-615d-4bf5-925c-9b782a32d393 SEQUENCE:3 CREATED:20231025T082843Z DESCRIPTION: Medições da produção¸ ao associada de bosões de Higgs com quarks top foram realizadas utilizando 139 fb−1 de dados recolhidos pela experiencia ATLAS no ˆ LHC. Eventos com um ou dois leptões no ˜ e stado final e compatíveis com o decaimento H → b ¯b foram selecionados . A secção eficaz de ˜ ttH¯ (H → b ¯b) foi medida de forma diferenc ial em bins do momento transverso do bosão de Higgs. Foi observado um exc esso de eventos relativamente a previsão do fundo com uma significância estatística de 1.0σ (2.7σ esperada). A força do sinal foi medida: 0.35 ± 0.20(stat.) +0.30 −0.28(syst.). As propriedades de cargaparidade (CP ) da interação de Yukawa entre o quark top e o bosão de Higgs foram med idas pela primeira vez no canal ttH/tH ¯ (H → b ¯b). Novas variáveis angulares foram utilizadas para distinguir entre cenários de CP. O valo r medido do ângulo de mistura de CP ˆ e´ 11◦+52◦ −73◦. Estudos focados no trigger da experiência ATLAS foram realizados. Para a Run 3\, triggers dedicados a medidas da produção exclusiva de pares de jatos\, c ombinando informação do detetor central e do AFP\, foram implementados. Para o HL-LHC\, o desempenho de um trigger de traços foi estudado. LAST-MODIFIED:20231025T143114Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/measurements-of-higgs-boson-p roperties-in-associated-production-with-top-quarks-with-the-atlas-detector / X-ALT-DESC;FMTTYPE=text/html:Medições da prod ução¸ ao associada de bosões de Higgs com quarks top foram realizadas utilizando 139 fb−1 de dados recolhidos pela experiencia ATLAS no ˆ L HC. Eventos com um ou dois leptões no ˜ estado final e compatíveis com o decaimento H → b ¯b foram selecionados. A secção eficaz de ˜ ttH¯ (H → b ¯b) foi medida de forma diferencial em bins do momento transver so do bosão de Higgs. Foi observado um excesso de eventos relativamente a previsão do fundo com uma significância estatística de 1.0σ (2.7σ es perada). A força do sinal foi medida: 0.35 ± 0.20(stat.) +0.30 −0.28(s yst.). As propriedades de cargaparidade (CP) da interação de Yukawa entr e o quark top e o bosão de Higgs foram medidas pela primeira vez no cana l ttH/tH ¯ (H → b ¯b). Novas variáveis angulares foram utilizadas par a distinguir entre cenários de CP. O valor medido do ângulo de mistura de CP ˆ e´ 11◦+52◦ −73◦. Estudos focados no trigger da experiên cia ATLAS foram realizados. Para a Run 3\, triggers dedicados a medidas da produção exclusiva de pares de jatos\, combinando informação do detet or central e do AFP\, foram implementados. Para o HL-LHC\, o desempenho d e um trigger de traços foi estudado.
END:VEVENT BEGIN:VEVENT SUMMARY:Optimization of materials for Metal-Isolador-Metal resistive devic es (Memristors) DTSTART:20231121T140000Z DTEND:20231121T160000Z DTSTAMP:20240329T082742Z UID:a5451f79-8024-4006-9975-940ebacb03fe SEQUENCE:2 CREATED:20231116T120842Z DESCRIPTION:Os computadores modernos\, baseados na arquitetura determinís tica de von Neumann\, onde a memória e o processamento estão fisicamente separados\, não conseguem aprender e adaptar-se a novos ambientes de man eira eficiente e prática. Assim\, é necessária uma nova abordagem\, e d ispositivos capazes de simultaneamente armazenar e processar informação são blocos essenciais de construção. O memristor é uma memória não v olátil de dois terminais baseada em estruturas metal-isolador-metal que e stabelece uma relação não-linear entre o histórico de corrente e tens ão por meio de comutação resistiva. Satisfaz os dois critérios de mem ória e computação\, sendo um candidato promissor para esta nova era de informação.Este trabalho centraliza-se na otimização do processo de mi crofabricação de dispositivos memristivos baseado em estrutura de Si/Ag\ , com configuração simples. Dois processos simples\, com pequenas altera ções\, consoante a caracterização dos dispositivos\, são implementado s onde o contacto à estrutura metal-insulador-metal é definida por litog rafia ótica e gravura por feixe de iões. Os vários dispositivos foram f abricados com os mesmos materiais\, esquiometria e técnicas de deposiçã o\, mas com espessuras do elétrodo de topo variáveis\, de 2 nm\, 5 nm\, e 10 nm de Ag. Os filmes finos e dispositivos microfabricados foram caract erizados eletricamente.Neste trabalho\, estudámos a comutação resistiva de estruturas metal-isolador-metal. Uma dinâmica do sistema Si/Ag\, PT/S i/Ag/TiW\, foi fabricada e caracterizada. O comportamento de comutação r esistiva bipolar observado é consistente com a formação e rutura de fil amentos metálicos de Ag. Si /Ag revelaram histerese bipolar que reivindic a o efeito de memória esperado em sistemas memristivos com resistividades baixas e rácio ROFF/RON ~1\, respetivamente. LAST-MODIFIED:20231121T111001Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/optimization-of-materials-for -metal-isolador-metal-resistive-devices-memristors/ X-ALT-DESC;FMTTYPE=text/html:Os computadores mod
ernos\, baseados na arquitetura determinística de von Neumann\, onde a me
mória e o processamento estão fisicamente separados\, não conseguem apr
ender e adaptar-se a novos ambientes de maneira eficiente e prática. Assi
m\, é necessária uma nova abordagem\, e dispositivos capazes de simultan
eamente armazenar e processar informação são blocos essenciais de const
rução. O memristor é uma memória não volátil de dois terminais basea
da em estruturas metal-isolador-metal que estabelece uma relação não-li
near entre o histórico de corrente e tensão por meio de comutação resi
stiva. Satisfaz os dois critérios de memória e computação\, sendo um c
andidato promissor para esta nova era de informação.
Este trabalho centraliza-se na otimização do process
o de microfabricação de dispositivos memristivos baseado em estrutura de
Si/Ag\, com configuração simples. Dois processos simples\, com pequenas
alterações\, consoante a caracterização dos dispositivos\, são imple
mentados onde o contacto à estrutura metal-insulador-metal é definida po
r litografia ótica e gravura por feixe de iões. Os vários dispositivos
foram fabricados com os mesmos materiais\, esquiometria e técnicas de dep
osição\, mas com espessuras do elétrodo de topo variáveis\, de 2 nm\,
5 nm\, e 10 nm de Ag. Os filmes finos e dispositivos microfabricados foram
caracterizados eletricamente.
Nest e trabalho\, estudámos a comutação resistiva de estruturas metal-isolad or-metal. Uma dinâmica do sistema Si/Ag\, PT/Si/Ag/TiW\, foi fabricada e caracterizada. O comportamento de comutação resistiva bipolar observado é consistente com a formação e rutura de filamentos metálicos de Ag. S i /Ag revelaram histerese bipolar que reivindica o efeito de memória espe rado em sistemas memristivos com resistividades baixas e rácio ROFF/RON ~ 1\, respetivamente.
END:VEVENT BEGIN:VEVENT SUMMARY:Testing entanglement and Bell inequalities at colliders DTSTART:20231121T160000Z DTEND:20231121T180000Z DTSTAMP:20240329T082742Z UID:8e1b2d23-3068-4c3d-9873-3d1206266528 SEQUENCE:1 CREATED:20231114T160132Z DESCRIPTION:Abstract:In this talk\, we explore the experimental prospects to measure the entanglement and violation of Bell inequalities at the LHC. In particular\, we will focus on two quantum systems: t-tbar pairs and ZZ produced from Higgs decay. LAST-MODIFIED:20231114T160132Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/testing-entanglement-and-bell -inequalities-at-colliders/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
In th
is talk\, we explore the experimental prospects to measure the entanglemen
t and violation of Bell inequalities at the LHC. In particular\, we will f
ocus on two quantum systems: t-tbar pairs and ZZ produced from Higgs decay
.
Nesta tese\, estuda mos extensões do Modelo Padrão no setor escalar\, em particular modelos com N dubletos de Higgs (NHDM).
Existe um gra
nde interesse em modelos com três dubletos de Higgs em que fermiões com
uma certa carga acoplam a um único e distinto campo de Higgs.
p>
Estudamos as diferenças fenomenológicas entr e as duas versões comuns deste 3HDM\, denominado tipo-Z. Salientamos que as diferenças entre os dois modelos surgem unicamente no potencial escala r.
Assim\, focamo-nos em observáveis que envo lvem apenas acoplamentos entre escalares.
Rev
elou-se difícil descobrir caracteristicas que diferenciem de forma única
a variante Z3 do modelo.
No entant o\, ao estudar a dependência do acoplamento trilinear do Higgs nas massas dos escalares ainda não observados\, conseguimos identificar alguns dos indicadores exclusivos da versão Z2xZ2 do 3HDM tipo-Z. Assim\, destaca-se a importância de medições de precisão do acoplamento trilinear do Hig gs.
Neste estudo\, e na restante literatura\, o 3HDM com simetria Z2xZ2 é considerado no caso de conservação explici ta de CP\, incluindo apenas parâmetros reais no potencial escalar.
De seguida\, apresentamos a parametrização físic
a do 3HDM com simetria Z2xZ2 geral\, com parâmetros complexos.
<
/p>
Demonstramos que o modelo complexo pode\, em princípio\, permitir um acoplamento h125bb totalmente pseudoescalar\, enq uanto que h125tt permanece totalmente real.
M ostramos também como implementar as restrições teóricas e fenomenológ icas de unitariedade\, BFB e STU\, preparando o trabalho necessário para um estudo do espaço de parâmetros deste modelo num trabalho futuro.
END:VEVENT BEGIN:VEVENT SUMMARY:Permanent Magnet Optimization for Nuclear Fusion Reactors DTSTART:20231122T140000Z DTEND:20231122T160000Z DTSTAMP:20240329T082742Z UID:4bd00ec4-ec6a-4371-9b92-d38fbc7eb6df SEQUENCE:2 CREATED:20231116T140906Z DESCRIPTION:A otimização de equilíbrios magnéticos revolucionou a inve stigação em stellarators equiparando-os aos tokamaks e trazendo este mod elo para o topo da fusão nuclear. No entanto\, não é suficiente obter e quilíbrios que apresentem resultados ótimos numericamente. É crucial ga rantir que possam ser reproduzidos com sistemas magnéticos reais. Embora o W7-X tenha sido bem-sucedido em demonstrar experimentalmente a viabilida de de stellarators otimizados\, o processo de construção das bobinas rev elou-se um grande desafio. Como tal\, a procura por formas alternativas de gerar equilíbrios stellarator altamente otimizados é de extrema import ância. Neste trabalho\, o módulo de otimização SIMSOPT é utilizado pa ra explorar o potencial dos ímanes permanentes como uma ferramenta comple mentar ou uma solução alternativa às bobinas modulares\, tendo duas apl icações em mente: o uso de ímanes permanentes como uma forma de corrigi r erros nos campos magnéticos de bobinas modulares e a possibilidade de c onverter um tokamak num stellarator. O primeiro tenta combinar as vantagen s dos ímanes permanentes com o conhecimento já estabelecido em bobinas m odulares. Demonstrou-se que os ímanes permanentes são uma ferramenta efi caz para a correção de campos de erro\, pelo menos até escalas e campo magnético comparáveis ao W7-X. O segundo representa uma forma de aumenta r o número de stellarators em operação\, acelerando a pesquisa em stell arators\, através da reutilização de componentes de tokamaks desativado s. Com o crescente interesse no conceito de stellarators\, esta poderia se r uma solução economicamente viável para permitir que mais centros de i nvestigação participem em novos estudos de energia a fusão. Um caso con creto\, o ISTTOK\, é analisado em detalhe\, determinando que opções ser iam viáveis na transformação deste tokamak num stellarator. LAST-MODIFIED:20231116T145115Z LOCATION:Sala P9 Pavilhão de Matemática\, Piso 2 URL:http://df.vps.tecnico.ulisboa.pt/eventos/permanent-magnet-optimization -for-nuclear-fusion-reactors/ X-ALT-DESC;FMTTYPE=text/html:A otimização de e
quilíbrios magnéticos revolucionou a investigação em stellarators <
/i>equiparando-os aos tokamaks e trazendo este modelo para o topo d
a fusão nuclear. No entanto\, não é suficiente obter equilíbrios que a
presentem resultados ótimos numericamente. É crucial garantir que possam
ser reproduzidos com sistemas magnéticos reais. Embora o W7-X tenha sido
bem-sucedido em demonstrar experimentalmente a viabilidade de stellara
tors otimizados\, o processo de construção das bobinas revelou-se um
grande desafio.
Como tal\, a procura por formas alternativas de
gerar equilíbrios stellarator altamente otimizados é de extrema
importância. Neste trabalho\, o módulo de otimização SIMSOPT é utiliz
ado para explorar o potencial dos ímanes permanentes como uma ferramenta
complementar ou uma solução alternativa às bobinas modulares\, tendo du
as aplicações em mente: o uso de ímanes permanentes como uma forma de c
orrigir erros nos campos magnéticos de bobinas modulares e a possibilidad
e de converter um tokamak num stellarator.
O prime
iro tenta combinar as vantagens dos ímanes permanentes com o conhecimento
já estabelecido em bobinas modulares. Demonstrou-se que os ímanes perma
nentes são uma ferramenta eficaz para a correção de campos de erro\, pe
lo menos até escalas e campo magnético comparáveis ao W7-X. O segundo r
epresenta uma forma de aumentar o número de stellarators em opera
ção\, acelerando a pesquisa em stellarators\, através da reutili
zação de componentes de tokamaks desativados.
Com o cre
scente interesse no conceito de stellarators\, esta poderia ser uma
solução economicamente viável para permitir que mais centros de invest
igação participem em novos estudos de energia a fusão. Um caso concreto
\, o ISTTOK\, é analisado em detalhe\, determinando que opções seriam v
iáveis na transformação deste tokamak num stellarator.
In the context of
the 4th Industrial Revolution\, paradigms are changing rapidly. Population
s growexponentially and thus more and more needs for security\, food\, nat
ural resources (especially water)\,electrical energy\, mobility\, health\,
sustainability\, among others\, are demanded. So\, it'\;s necessary t
odeepen concepts and develop technologies that can accommodate and integra
te such aspects.
Recently\, a lot of progress has been made in re
lation to energy matrices\, mainly due to allegationsrelated to fossil mat
rices\, said to contribute to some degree for the accumulation and transpo
rt ofheat outside of previous patterns in the biosphere. This strengthens
the discussion about thegeneration\, storage and use of energy. In this re
gard\, Brazil has been privileged by its great water\,biomass\, solar and
wind potential.
It provides the emergence of multiple business p
latforms aroundthese resources\, with low environmental impact. Furthermor
e\, with renewed strategic guidance inthis field and a very competitive av
ailability of mineral resources with high added value for theseapplication
s. It includes reserves of graphite\, niobium\, rare earths and lithium\,
materials that haveattracted growing interest in this regard.
Th
e needs of the electric aircraft market and their energyand power requirem
ents are raised\, and compared with storage devices already commercialized
or inthe prototype phase. Using electrodes based on niobium\, graphene an
d lithium MXenenanomaterials to the development of battery and supercapaci
tor packs\, the aim is to disrupt theoperation of small mockups in order t
o have them for future eVTOL and UAV technologies\, above thelimits of cur
rent devices.
The challenge surpasses the automotive one because
there are several waysof transferring momentum. So\, energy and power con
sumption can vary greatly depending on them(flat flight\, takeoff\, landin
g\, angular turns\, stall and others)\, in addition to subsystems containe
dtherein.
Está demonstrado q
ue um modelo com três dubletos de Higgs (3HDM) sob uma simetria A4 exata
não é compatível com massas de quarks diferentes de zero e/ou uma matri
z CKM não diagonal por blocos.
Nesta tese\, provamos que um 3HD
M com termos A4 softly broken no potencial escalar permite um fit às matr
izes de massa dos quarks. Além do mais\, o resultado é consistente com m
h=125 GeV e as medições de h→WW\,ZZ .
São também testadas
outras simetrias maiores do potencial escalar verificando-se que\, embora
permitissem o mesmo vev\, são inviabilizadas pelo setor de Yukawa. Como r
esultado secundário\, corrigimos uma lista de simetrias do 3HDM presente
na literatura. Verificamos\, ainda\, numericamente que\, para cada ponto q
ue obedece a todos os constrangimentos impostos\, o mínimo é um mínimo
global do potencial.
This master thesis
delves into the realm of neuromorphic computing\, a promising paradigm shi
ft poised to overcome the limitations of traditional von Neumann computer
architectures in the field of neural network algorithms. The focus is squa
rely placed on the memristor\, a non-volatile memory device that emulates
the behavior of synapses in the human brain\, offering a scalable and effi
cient alternative for computing systems. Through rigorous exploration of d
esign\, fabrication\, characterization\, and simulation aspects\, this dis
sertation evaluates the practicality of incorporating memristive devices i
nto neuromorphic computing systems.
The research is framed around a multi-faceted approach that includes the
innovation of tools and computational frameworks\, with a highlight being
the development of a pioneering software platform that synergistically int
egrates the capabilities of LT-Spice and Python. A characterization softwa
re\, "\;PyCharMem"\;\, has been developed to streamline the charac
terization process\, making it more accessible and scalable. Additionally\
, a portable probe station was conceived and manufactured\, addressing spa
ce constraints.
A total of 19 disti nct memristive devices were subjected to electrical characterization\, fac ilitating the extraction of their critical properties. This exhaustive ana lysis laid the groundwork for their emulation using SPICE models\, navigat ing the complexities through a genetic optimization algorithm tailored to extract intricate parameters. The research culminates in the execution of single-layer neural network simulations\, employing a gradient descent lea rning algorithm through a reputable SPICE simulator\, ensuring a comprehen sive and reliable evaluation of sneak paths in memristor crossbars.
END:VEVENT BEGIN:VEVENT SUMMARY:Particle Physics anomalies from Dark Matter DTSTART:20231122T160000Z DTEND:20231122T180000Z DTSTAMP:20240329T082742Z UID:24a92d22-24b1-4b8a-af39-df17652326df SEQUENCE:2 CREATED:20231116T151129Z DESCRIPTION:O Modelo Padrão é uma das teorias mais bem sucedidas da hist ória. Ainda assim\, algumas das suas previsões\, como é o caso do momen to magnético anómalo do muão\, estão em desacordo com as medições ex perimentais. Há também fenómenos observados que nem são descritos por esta teoria\, como é o caso da Matéria Escura. Uma solução habitual é adicionar novas partículas ao Modelo Padrão\, cujas propriedades devem ser capazes de explicar as discrepâncias\, sem comprometer outras previs ões do Modelo Padrão que já se encontram de acordo com as respetivas me dições experimentais. Nesta tese\, as correções radiativas aos Observ áveis de Precisão Electrofracos associados ao bosão Z são estudados e\ , consequentemente\, utilizados para restringir o espaço de parâmetros d e tais extensões. Fórmulas explícitas para os desvios dos observáveis no polo do Z em relação à previsão do Modelo Padrão são deduzidas\, considerando extensões com números arbitrários de escalares e fermiões . Quando utilizados num modelo promissor seleccionado da literatura\, este s observáveis diminuíram eficazmente o espaço de parâmetros permitido\ , com o novo observável (Reμ) a provocar as maiores restrições. Estes resultados realçam a importância de considerar os observáveis do polo d o Z ao trabalhar com extensões do Modelo Padrão que visam explicar a ori gem da Matéria Escura\, enquanto resolvem a discrepância na medição do momento magnético anómalo do muão. Parte deste trabalho foi submetido para publicação [1]. LAST-MODIFIED:20231116T151253Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/particle-physics-anomalies-fr om-dark-matter/ X-ALT-DESC;FMTTYPE=text/html:O Modelo Padrão é
uma das teorias mais bem sucedidas da história. Ainda assim\, algumas da
s suas previsões\, como é o caso do momento magnético anómalo do muão
\, estão em desacordo com as medições experimentais. Há também fenóm
enos observados que nem são descritos por esta teoria\, como é o caso da
Matéria Escura. Uma solução habitual é adicionar novas partículas ao
Modelo Padrão\, cujas propriedades devem ser capazes de explicar as disc
repâncias\, sem comprometer outras previsões do Modelo Padrão que já s
e encontram de acordo com as respetivas medições experimentais.
Nesta tese\, as correções radiativas aos Observáveis de Precisão Ele
ctrofracos associados ao bosão Z são estudados e\, consequentemen
te\, utilizados para restringir o espaço de parâmetros de tais extensõe
s. Fórmulas explícitas para os desvios dos observáveis no polo do Z<
/i> em relação à previsão do Modelo Padrão são deduzidas\, considera
ndo extensões com números arbitrários de escalares e fermiões.
Quando utilizados num modelo promissor seleccionado da literatura\, est
es observáveis diminuíram eficazmente o espaço de parâmetros permitido
\, com o novo observável (Reμ) a provocar as maiores restrições. Estes
resultados realçam a importância de considerar os observáveis do polo
do Z ao trabalhar com extensões do Modelo Padrão que visam explic
ar a origem da Matéria Escura\, enquanto resolvem a discrepância na medi
ção do momento magnético anómalo do muão. Parte deste trabalho foi su
bmetido para publicação [1].
Na natureza\, os qu
arks não podem existir por si mesmos. Quando são produzidos\, como\, por
exemplo\, em colisões de alta energia\, os quarks juntam-se a outros qua
rks para formar hádrons. Esse processo\, conhecido como hadronização\,
é impulsionado pela força forte (QCD) e ainda não é completamente comp
reendido. Medidas dos mésons B em colisores oferecem sondas únicas do pr
ocesso de hadronização\, pelo qual os quarks individuais formam hádrons
de cor neutra.
Neste trabalho\, os sinais dos mésons $B^{+}$ e $B^{0}_{s}$ são estudados e identificados n as colisões do LHC\, utilizando métodos avançados de machine learning.< /p>
Os mésons B são reconstruídos através dos
canais de decaimento $B^{+} \\rightarrow J/\\psi ~K^{+} \\rightarrow \\mu
^{+}\\mu^{-}K^{+}$ e $B^{0}_{s} \\rightarrow J/\\psi ~\\phi \\rightarrow \
\mu^{+}\\mu^{-}K^{+}K^{-}$\, em dados de colisões pp a uma energia de $\\
sqrt{s}=5\,02$ TeV coletados pelo experimento Compact Muon Solenoid (CMS)
no LHC.
Esta tese abrange todo o tr
abalho desenvolvido que engloba uma análise completa. Isso inclui a sele
ção de eventos\, realizada aqui utilizando o pacote XGBoost para a cria
ção de um modelo de boosted decision tree\, ajuste de parâmetros das di
stribuições de massa invariante obtidas e determinação da eficiência
do detetor e seleção\, na qual aplicamos um método inovador que minimiz
a a dependência da cinemática de MC e remove a contaminação de backgro
und na região de sinal. Também apresentamos comparações de desempenho
entre os modelos BDT e redes neurais (NN)\, juntamente com estudos que vis
am investigar a região de menor $p_T$\, sendo esta mais desafiadora.
Com estes ingredientes\, medimos a diff
erential production cross section dos mésons B em função das variáveis
cinemáticas de sinal (momento transversal e rapidez) e variáveis de amb
iente (multiplicidade de partículas carregadas)\, obtendo resultados cons
istentes com as previsões teóricas FONLL e resultados anteriores. Calcul
amos as razões das cross section entre os dois mésons B\, investigando a
s dependências da razão de fração de fragmentação\, $f_s/f_u$\, ness
as variáveis.
Os resultados fornec em indícios de um aumento na produção de $B^0_s$ em relação ao $B^+$ em multiplicidades de partículas carregadas elevadas\, como seria esperad o ao considerar a coalescência de quarks como um mecanismo complementar d e hadronização.
END:VEVENT BEGIN:VEVENT SUMMARY:Numerical evolution of well-posed field theories with anisotropic scaling DTSTART:20231123T143000Z DTEND:20231123T160000Z DTSTAMP:20240329T082742Z UID:8e6ebc9b-440e-40df-9fe7-82b9f0c00b17 SEQUENCE:2 CREATED:20231121T113350Z DESCRIPTION:ABSTRACT: Dynamical equations exhibiting an anisotropic scalin g between space and time admit a dispersive nature\, as they contain highe r-order spatial derivatives\, but remain second order in time. This is the case of a class of Lorentz-violating theories of gravity\, and this featu re results inconvenient for performing long-time numerical evolutions with standard explicit schemes. In this talk I will introduce a nobel scheme w hich is implicit\, stable and second-order accurate\, for sufficiently lar ge time steps. As a proof of concept\, we will apply it for evolving the L ifshitz scalar field on top of a spherically symmetric black hole space-ti me. Our results indicate that the dispersive terms produce a cascade of mo des that accumulate in the region in between the Killing and universal hor izons\, indicating a possible instability of the latter. LAST-MODIFIED:20231121T114512Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/numerical-evolution-of-well-p osed-field-theories-with-anisotropic-scaling/ X-ALT-DESC;FMTTYPE=text/html:ABSTRACT: Dynamical
equations exhibiting an anisotropic scaling between space and time admit
a dispersive nature\, as they contain higher-order spatial derivatives\, b
ut remain second order in time. This is the case of a class of Lorentz-vio
lating theories of gravity\, and this feature results inconvenient for per
forming long-time numerical evolutions with standard explicit schemes.
In this talk I will introduce a nobel scheme which is implicit\, st
able and second-order accurate\, for sufficiently large time steps. As a p
roof of concept\, we will apply it for evolving the Lifshitz scalar field
on top of a spherically symmetric black hole space-time. Our results indic
ate that the dispersive terms produce a cascade of modes that accumulate i
n the region in between the Killing and universal horizons\, indicating a
possible instability of the latter.
Abstract:
There
may exist B-L violating interactions which can be at the origin of baryon
asymmetry both in the visible and dark sectors in the early universe\, an
d they can also induce the mixing phenomena of the neutral ordinary partic
les with dark particles. I discuss how such interactions can produce antin
uclei in the present universe. In fact\, AMS-2 experiment has detected eig
ht antihelium candidates and can be explained by this mechanism which
also suggests that the heavier antinuclei as anticarbon or antioxygen may
also exist in cosmic rays.
Estudar a eletrofisiologia do coração é uma tentativa de c
ompreender a essência da sua função. Analisar um eletrocardiograma (ECG
) é interpretar a atividade elétrica do coração\, permitindo a deteç
ão de anomalias na condução cardíaca. A fibrilação atrial (FA)\, um
tipo particular de arritmia\, é causada pela atividade elétrica involunt
ária na aurícula esquerda do coração. Como consequência\, a propagaç
ão do sinal cardíaco é prejudicada\, afetando a sua velocidade de condu
ção.
O objetivo final desta tese é criar um modelo que possa
analisar o ECG\, classificar o seu estado e estimar a velocidade média de
condução do sinal atrial. Para atingir este objetivo\, foram selecionad
os pacientes com FA submetidos a ablação cardíaca (um tratamento para a
FA) no Departamento de Cardiologia do Hospital de Santa Marta\, e os dado
s de ECG de 12 derivações\, registados antes e após o procedimento de a
blação foram analisados.
Em seguida\, comparámos os dados do
ECG de pacientes e de indivíduos saudáveis e estimámos as respetivas ve
locidades de condução. A abordagem resultou em modelos de Machine Learni
ng e de Deep Learning que podem distinguir com precisão entre os dados de
ECG de pacientes antes e depois da ablação e dados de indivíduos saud
áveis. Através de várias abordagens testadas\, uma rede neural artifici
al com duas camadas ocultas simples superou todos os seus concorrentes\, d
istinguindo os conjuntos de dados com uma precisão máxima de $96\,90\\%$
. O seu desempenho foi seguido pelo algoritmo Random Forest\, que se revel
ou o melhor ajuste entre os modelos de Machine Learning implementados. Um
algoritmo de Decision Tree foi optimizado\, proporcionando os melhores res
ultados para a estimativa das velocidades.
O modelo foi capaz de
estimar uma velocidade média de condução do sinal atrial de 60\,86 ±
10\,79 cm/s para os indivíduos saudáveis e um valor de 41\,62 ± 20\,36
cm/s para os pacientes antes da ablação. Os resultados da Decision Tree\
, reforçados pela correlação observada da característica extraída &qu
ot\;Positive Slope V1"\;\, que representa a inclinação da variação
positiva da onda P\, encontrada no canal V1 do ECG de 12 derivações\, d
ão fortes indícios de que esta característica reflete a velocidade de c
ondução do sinal atrial.
Abstract: Cl
assical kinetic theory is a very successful tool to understand the dynamic
s of many-body systems that display low degeneracy and low-to-moderate cor
relation degree. In particular\, the behavior of high-temperature plasmas
is very well captured using classical kinetic theory\, for which the latte
r assumptions are particularly valid.
However\, as the microscop
ic details of the interactions become more and more important\, as well as
quantum degeneracy and/or correlations start to play a role\, the resulti
ng equations loose their validity\, and ab initio quantum approache
s are required.
In this talk\, I will discuss recent result
s of the application of quantum kinetic theory to study the interactions b
etween matter and radiation in terms of Wigner functions. I will start by
introducing the main features of kinetic theories (both classical and quan
tum)\, and analyze their validity.
The case of a quantum plasma
will be examined in detail. Then\, as an application\, I will discuss phot
on condensation in plasmas and photon turbulence in cold atoms.
A Drosophila mel
anogaster é essencial para compreender a macroevolução ao nível mo
lecular. O objectivo desta tese é a construção de um modelo matemático
que descreva a expressão de dois genes pair-rule\, eve e ftz
i>\, fundamentais na formação de segmentos na fase embriónica da Drosop
hila. Começamos por derivar um sistema base que define os mecanismos nece
ssários no controlo da transcrição de um gene: produção livre de uma
proteína\, ativação e repressão.
Considerando um argumento p
uramente termodinâmico\, a lei de massa-acção\, propomos uma definiçã
o da região segmentada pelas proteínas terminais Tll e Hkb
e uma regulação individual de riscas do padrão do Eve com cinco
promotores essenciais. O modelo de cada promotor é testado contra os dad
os experimentais\, e optimizado com recurso a um algoritmo de Monte Carlo.
Considerando uma transcrição heterogénea do mRNA ao longo do embrião\
, calibramos espacialmente a taxa de produção de Eve.
A
mesma estratégia cinética foi utilizada na identificação de três pro
motores\, e respectivos reguladores\, do ftz. Alcançamos com suces
so a calibração dos padrões do Eve e Ftz\, revelando como
as duas proteínas se podem desenvolver de forma totalmente independente\
, com uma “leitura” diferenciada dos mesmos conjuntos de fatores gap r
epressivos. Exploramos ainda um conceito alternativo de repressão direta
entre o Eve e o Ftz\, mostrando como este é suficiente para
explicar a formação do padrão perfeitamente complementar do Ftz
. Por fim\, provamos que a regulação dos genes segment-polarity é bem d
escrita por um modelo cinético de massa-acção.
Motivados pelas dis
crepâncias em observáveis relacionados com o decaimento do mesão-B entr
e outros resultados conhecidos como Lepton Flavour Universality\, f
oram propostas uma classe de modelos que resolvem o problema pela adição
de novos campos um dos quais é um candidato a matéria escura. Os novos
campos geram diagramas com partículas de matéria escura ao nível quânt
ico que resolvem a discrepância entre o valor medido do g-2 do muão e o
cálculo teórico do Modelo Padrão (MP).
Esta solução é acom
panhada por um número de escalares com cor que interagem com o bosão de
Higgs do MP. Neste projeto\, calculamos as contribuições de primeira ord
em para a secção eficaz de um Higgs e dois Higgs padrão\, no Large H
adron Collider (LHC) com uma energia do centro de massa de 14 TeV. Os
cálculos analíticos são implementando em dois programas relacionados co
m a produção de Higgs\, HIGLU e HPAIR.
Tomando em conta as bus
cas por escalares com cor no LHC apenas consideramos massas pesadas. Em pa
rticular\, exploramos massas no intervalo entre 0.8 TeV e 5.0 TeV. Os resu
ltados são usados\, em conjunto com os limites experimentais atuais mais
relevantes\, para restringir o espaço de parâmetros das massas dos escal
ares e dos seus acoplamentos ao bosão de Higgs. Consideramos também os l
imites projetados em futuras experiências\, tais como o projecto do LHC d
e alta-luminosidade (HL-LHC).
Neste trabalho\, tu
bos de β-Ga2O3\, exfoliados a partir de um cristal em orientação (100)
com uma nova técnica de exfoliação assistida por feixe de iões\, foram
usados para criar dispositivos para testar como fotodetetores e transíst
ores de efeito de campo (FET). Primeiramente\, o processo de fabricação
dos dispositivos foi otimizado.
Este inclui a transferência de
tubos para um novo substrato\, um passo de recozimento no qual estes se de
senrolam em membranas\, a colocação de máscaras de sombra e a deposiç
ão de contactos elétricos. Os contactos seriam também otimizados e\, pa
ra contactos de Ti/Au\, foi encontrada uma temperatura ótima para a obten
ção de contactos óhmicos por volta dos 500 °C\, para recozimentos em a
tmosfera de N2\, em concordância com a literatura.
Os dispositi
vos testados como fotodetetores provaram não ser insensíveis ao espetro
solar (solar blind)\, mas mostraram respostas distintas nos casos e
m que os contactos são iluminados diretamente ou em que apenas a membrana
recebe luz direta. Foram efetuadas medidas transientes\, com tempos de re
sposta da ordem de 1 s medidos para a luz de uma lâmpada de deutério.
O dispositivo testado como FET encontrava-se em modo de depleção
\, com uma tensão de limiar de -23\,2 V e um rácio on/off de 8600
para uma tensão de -10 V entre dreno e fonte. Como interruptor\, o FET m
ostrou um tempo de resposta substancialmente mais baixo do que o tempo ent
re medidas\, sendo este cerca de 1 s\, bem como uma excelente estabilidade
após 500 repetições.
Resumo
Os previsíveis efeitos drásticos das alteraçõe
s climáticas no planeta impelem à mobilização de esforços e criação
de compromissos que possam levar à concretização de uma célere e efic
az transição energética. Esta estará\, inegavelmente\, ligada a altera
ções nos padrões de consumo e geração de eletricidade e\, invariavelm
ente\, alicerçada na aposta em fontes de energia renováveis. Neste senti
do\, as comunidades de energia assumem-se como uma ferramenta útil ao ser
viço do cumprimento de metas ambientais\, enquanto permitem a gestão aut
ónoma e descentralizada de energia\, com potenciais benefícios económic
os para os seus participantes.
Nest
e trabalho\, é avaliada a possibilidade de criação de uma comunidade de
energia composta por edifícios públicos e residenciais\, que poderá be
neficiar de intervenção do Município. São estudados os perfis de consu
mos elétricos\, as condições de geração de energia através de painé
is fotovoltaicos em diferentes cenários e a utilização de sistemas de a
rmazenamento. Por fim\, são criados vários cenários de mercados locais
de energia\, testando modelos de agregação e transações peer-to-peer.<
br/>
Os resultados sugerem que modelos d e transação peer-to-peer apresentam benefícios para os participantes\, embora a presença de um agregador não seja universalmente vantajosa. Des te modo\, um conjunto de participantes poderá operar gerido por um agrega dor\, eventualmente designado pelo Município\, enquanto os restantes cons ervam maior autonomia. Além disso\, a comunidade de energia proposta prom ove consideráveis níveis de auto-consumo e auto-suficiência\, ao mesmo tempo que presta um contributo relevante para a redução de emissões de gases com efeito de estufa.
END:VEVENT BEGIN:VEVENT SUMMARY:Reinforcement Learning for Battery Operation: Energy Arbitrage Con sidering Battery Degradation DTSTART:20231127T160000Z DTEND:20231127T180000Z DTSTAMP:20240329T082743Z UID:b0a6f1ca-3553-438b-8f12-38517b0532b4 SEQUENCE:2 CREATED:20231123T154117Z DESCRIPTION:Os sistemas de armazenamento de energia (BESS) proporcionam ao s seus proprietários maior controlo sobre o uso de energia. Realizando ar bitragem de energia (EA)\, os proprietários conseguem reduzir as suas des pesas energéticas. Contudo\, a maioria carece do conhecimento necessário para optimizar estes sistemas para EA. Neste tipo de ambientes de sistema de energia dinâmicos\, a aprendizagem por reforço (RL) destaca-se como uma poderosa ferramenta de tomada de decisão\, capaz de maximizar os lucr os alcançáveis por EA. Todavia\, o desempenho de uma bateria é inconsta nte\, porque a sua capacidade diminui progressivamente. É fundamental tom ar em conta esta degradação da bateria para obter resultados fiavéis\, pois pode prejudicar potenciais lucros de EA\, talvez mais ainda se for de sconsiderada. Este trabalho utiliza RL para encontrar a forma ideal de ope rar uma bateria que fornece serviços de EA residencial\, considerando a d egradação da bateria prevista por um modelo de aprendizagem semi-supervi sionada. Analisam-se três cenários: um onde o algoritmo é treinado numa bateria com capacidade máxima constante irrealista\, um que considera a capacidade real ao longo da vida da bateria e calcula o verdadeiro resulta do das decisões tomadas no primeiro cenário\, e um onde o algoritmo é t reinado numa bateria com capacidade real decrescente. Os resultados mostra m que\, se a degradação for desconsiderada durante a operação da bater ia\, os custos de degradação reduzem potenciais lucros em 13%. Se consid erada\, esta percentagem cai para 4%. Ter em conta a degradação pode tam bém aumentar a vida da bateria em 20%\, adiando a sua substituição e in vestimentos associados. LAST-MODIFIED:20231124T092454Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/reinforcement-learning-for-ba ttery-operation-energy-arbitrage-considering-battery-degradation/ X-ALT-DESC;FMTTYPE=text/html:Os sistemas de arma
zenamento de energia (BESS) proporcionam aos seus proprietários maior con
trolo sobre o uso de energia. Realizando arbitragem de energia (EA)\, os p
roprietários conseguem reduzir as suas despesas energéticas. Contudo\, a
maioria carece do conhecimento necessário para optimizar estes sistemas
para EA. Neste tipo de ambientes de sistema de energia dinâmicos\, a apre
ndizagem por reforço (RL) destaca-se como uma poderosa ferramenta de toma
da de decisão\, capaz de maximizar os lucros alcançáveis por EA.
<
br/>Todavia\, o desempenho de uma bateria é inconstante\, porque a sua ca
pacidade diminui progressivamente. É fundamental tomar em conta esta degr
adação da bateria para obter resultados fiavéis\, pois pode prejudicar
potenciais lucros de EA\, talvez mais ainda se for desconsiderada.
Este trabalho utiliza RL para encontrar a forma ideal de operar uma bat
eria que fornece serviços de EA residencial\, considerando a degradação
da bateria prevista por um modelo de aprendizagem semi-supervisionada. An
alisam-se três cenários: um onde o algoritmo é treinado numa bateria co
m capacidade máxima constante irrealista\, um que considera a capacidade
real ao longo da vida da bateria e calcula o verdadeiro resultado das deci
sões tomadas no primeiro cenário\, e um onde o algoritmo é treinado num
a bateria com capacidade real decrescente.
Os resultados mostram
que\, se a degradação for desconsiderada durante a operação da bateri
a\, os custos de degradação reduzem potenciais lucros em 13%. Se conside
rada\, esta percentagem cai para 4%. Ter em conta a degradação pode tamb
ém aumentar a vida da bateria em 20%\, adiando a sua substituição e inv
estimentos associados.
Desde a década de
70\, o Modelo Padrão (SM) da física de partículas assegurou uma descri
ção precisa da interação eletrofraca e da força nuclear forte. No ent
anto\, a deteção de oscilações de neutrinos leves entra em conflito co
m a falta de termos de massa de neutrinos nesta teoria. A extensão da mes
ma a neutrinos estéreis pode corrigir o problema através do mecanismo se
esaw tipo I.
Os modelos seesaw testáveis em colisores são gera
lmente protegidos por uma simetria semelhante ao número leptónico\, faze
ndo com que leptões neutros pesados (HNLs) apareçam como pares neutrino-
antineutrino pseudo-Dirac.
Tal como os mesões neutros\, estes podem o
scilar entre estados de partícula-antipartícula\, provocando a violaçã
o do número leptónico (LNV). Recentemente\, a análise de Monte Carlo de
monstrou que o Grande Colisor de Hadrões (LHC) é capaz de investigar est
e fenómeno.
Colisores de leptões\, como o Futuro Colisor C
ircular de e+e- (FCC-ee)\, serão cruciais na procura de neutrinos long-li
ved. Este trabalho discute a sua capacidade no estudo de LNV através de o
scilações de neutrinos-antineutrinos pesados (NNOs). Para tal\, demonstr
ou-se que distribuições de observáveis\, como a assimetria forward-back
ward dos HNLs e o momento dos respetivos produtos de decaimento\, desenvol
vem dependência oscilatória no tempo de vida dos HNL.
Este
s sinais\, possivelmente resolúveis para HNLs long-lived\, contêm inform
ação sobre a geração de massa de neutrinos e permitem a descoberta de
LNV. Mesmo quando não são diretamente observáveis\, estas propriedades
podem ser investigadas através das distribuições integradas no tempo. O
s resultados mostram que NNOs devem-se incluir nas simulações de HNLs no
FCC-ee.
Abstract: Re
centemente\, a área de processamento de informação quântica (QIP) tem-
se vindo a tornar progressivamente mais popular à medida que mais aplica
ções com relevância prática para a sociedade são desenvolvidas. Isto
resulta num aumento da procura por profissionais com conhecimento de QIP\,
que as faculdades têm dificuldade a acompanhar\, uma vez que experiênci
as de QIP requerem instrumentação altamente especializada e complexa. Is
to faz com que RMN seja uma plataforma atrativa para introduzir estudantes
a QIP experimental\, pois a maioria das universidades disponibiliza acess
o a espetrómetros de RMN. Este trabalho consiste numa introdução experi
mental a QIP em RMN líquido.
Duas
amostras de clorofórmio líquido são usadas\, uma reforçada com 13C e o
utra com 12C\, que correspondem a sistemas de 2-qubits e 1-qubit\, respeti
vamente. Começa-se por apresentar a teoria de QIP de 1 e 2-Qubits em RMN
líquido\, descrevendo a preparação de estados pseudo-puros\, a implemen
tação de portas lógicas quânticas de 1 e 2 qubits e o mecanismo de lei
tura. Quanto à parte experimental\, implementa-se diversas portas de 1-qu
bit no sistema de 1-qubit.
No sistema de 2-qubits\, mede-se os t
empos de relaxação T1\, T2 e T2* e faz-se experiências onde se implemen
ta a porta CNOT\, e unitários de geração de entrelaçamento quântico e
de transferência quântica de estados\, obtidos a partir de uma CTQW em
quadrados de lados sinalizados. As experiências de implementação de por
tas de 1-qubit e CNOT indicam que temos experimentalmente universalidade d
e portas de 2-qubits. Um pacote de Mathematica foi desenvolvido com funcio
nalidades que apoiam o trabalho teórico e experimental.
No panorama da revo
lução da "\;Internet das Coisas"\; (IoT)\, a necessidade de sens
ores compactos\, robustos e energeticamente eficientes torna-se cada vez m
ais crítica. Entre os sensores magnéticos\, os sensores TMR perpendicula
res (OOP) destacam-se pelo seu potencial de oferecer uma relação sinal-r
uído significativamente melhor\, excelente escalabilidade e uma robusta e
stabilidade térmica. Além disso\, à medida que a procura para melhorar
a deteção em várias aplicações persiste\, a versatilidade e adaptabil
idade dos sensores OOP TMR na afinação da sua linearidade e sensibilidad
e anunciam um futuro promissor deste tipo de sensores.
Para compreender e otimizar sensores magnéticos OOP
para aplicações específicas\, um estudo abrangente foi conduzido\, divi
dido em simulações e fabricações práticas. Utilizando simulações mi
cromagnéticas de diferenças finitas\, o comportamento magnético destes
sensores foi extensivamente estudado. Isto ajudou a compreender a interaç
ão RKKY\, o acoplamento de troca interfacial e as anisotropias volumétri
cas\, além de fornecer uma compreensão detalhada do comportamento depend
ente da temperatura e dos parâmetros de design para requisitos específic
os.
No INESC MN\, sensores OOP reai s foram fabricados e caracterizados utilizando um novo dispositivo constru ído. Este dispositivo permite leituras de sensores simultâneas\, permiti ndo assim a recolha em massa de dados para análises estatísticas mais co nfiáveis. Estas caracterizações concluíram que a melhor temperatura de annealing se situa perto dos 300ºC\, onde alguns sensores alcançaram um efeito magnetoresistivo (MR) de quase 60\\%. Este estudo também revelou a dependência de parâmetros importantes\, como a linearidade e coercivid ade destes sensores em função da espessura e geometria do CoFeB.
END:VEVENT BEGIN:VEVENT SUMMARY:Developing partial-volume multi-beam FLASH with Proton Beams DTSTART:20231129T130000Z DTEND:20231129T150000Z DTSTAMP:20240329T082743Z UID:88ee6ecf-223d-4f3f-90ab-632b04b2cba3 SEQUENCE:2 CREATED:20231129T111341Z DESCRIPTION:Abstract:The work for this doctoral research has been mainly d eveloped at the German Cancer Research Center (DKFZ)\, Heidelberg\, German y\, and at the Centro de Protonterapia Quirón salud (CPT)\, Madrid\, Spai n\, with support from the Laboratório de Instrumentação e Física Exper imental de Partículas (LIP)\, Lisbon\, Portugal.The main purpose of this work is to investigate how to implement multi-beam FLASH technique in prot on radiotherapy\, going from simulations using the treatment planning tool -kit MATRAD\, to a clinical application with Raystation (RaySearch Laborat ories\, Stockholm\, Sweden)\, a commercial treatment planning system (TPS) \, and delivery in with a ProteusOne protontherapy system (Ion Beam Applic ations\, Leuven\, Belgium). LAST-MODIFIED:20231129T111400Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/developing-partial-volume-mul ti-beam-flash-with-proton-beams/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
The w
ork for this doctoral research has been mainly developed at the German Can
cer Research Center (DKFZ)\, Heidelberg\, Germany\, and at the Centro de P
rotonterapia Quirón salud (CPT)\, Madrid\, Spain\, with support from the
Laboratório de Instrumentação e Física Experimental de Partículas (LI
P)\, Lisbon\, Portugal.
The main purpose of this work is to inves
tigate how to implement multi-beam FLASH technique in proton radiotherapy\
, going from simulations using the treatment planning tool-kit MATRAD\, to
a clinical application with Raystation (RaySearch Laboratories\, Stockhol
m\, Sweden)\, a commercial treatment planning system (TPS)\, and delivery
in with a ProteusOne protontherapy system (Ion Beam Applications\, Leuven\
, Belgium).
Abstract: O
n Mars\, the atmosphere plays a pivotal role in the In-Situ Resourc
e Utilization (ISRU) perspective\, mainly due to the abundant atmospheric
CO2. Plasma technologies\, especially the application of low-temperature p
lasmas (LTPs)\, have been proposed to decompose the existing CO2\, facilit
ating the recovery of O2 and CO to support life\, fuel\, and agriculture.
However\, much remains to be done regarding accurate plasma modeling\, whi
ch relies on the availability of precise reaction rate coefficients. Deter
mining these constants is a non-trivial task\, primarily addressed by scie
ntists with extensive experience in the field.
In this thesis\, we investigate the use of machine learning te
chniques to predict these parameters. This is done with an automated and s
ystematic approach\, based on the heavy-species densities of the gas'\
;s final state. The training data is generated using the Lisbon Kinetics s
imulation tool (LoKI).
Both Support Vector Regression (SVR) and Artificial Neural Network (ANN) models were t rained using an oxygen (O2) plasma kinetic scheme\, encompassing 11 specie s and 53 heavy-species reaction processes. When evaluated on a test datase t\, the top performing SVR and ANN models achieved mean relative error val ues of 0.10% and 0.22%\, respectively. Although both models exhibited sign ificant accuracy\, the SVR model emerged as superior\, offering both simpl icity and heightened performance for our specific low-dimensional dataset. These two machine learning approaches serve as a successful preliminary s tep towards more comprehensive models to automate the prediction of reacti on rate coefficients.
END:VEVENT BEGIN:VEVENT SUMMARY:Premises of signal beyond the Standard Model ? Run2 results from t he ML based search of supersymmetric top DTSTART:20231129T143000Z DTEND:20231129T160000Z DTSTAMP:20240329T082743Z UID:06299c1e-acff-4fc5-bf26-3fad847efccb SEQUENCE:1 CREATED:20231128T095931Z DESCRIPTION:Abstract:The LHC machine has delivered an unprecedented number of proton proton collisions at 13 TeV\, so far our best window to look fo r phenomena beyond the Standard Model (SM) of particle physics. The search for the lightest supersymmetric top (stop) has been one of the most motiv ated search directions during the Run2 of the LHC.In this talk\, I will pr esent the latest results of the CMS collaboration on the search for the st op decaying in four bodies. This decay mode\, where the observable particl es can be extremely soft\, is very challenging\, while motivated by measur ements of the cold dark matter. The search is harnessed on a Machine Learn ing approach\, which is adapted to different signal masses. I will scrutin ize the observation of a 2.5 sigma excess of data versus the predicted SM background\, and briefly cover perspectives for this search. LAST-MODIFIED:20231128T095931Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/premises-of-signal-beyond-the -standard-model-run2-results-from-the-ml-based-search-of-supersymmetric-to p/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
The L
HC machine has delivered an unprecedented number of proton proton collisio
ns at 13 TeV\, so far our best window to look for phenomena beyond the Sta
ndard Model (SM) of particle physics. The search for the lightest supersym
metric top (stop) has been one of the most motivated search directions dur
ing the Run2 of the LHC.
In this ta lk\, I will present the latest results of the CMS collaboration on the sea rch for the stop decaying in four bodies. This decay mode\, where the obse rvable particles can be extremely soft\, is very challenging\, while motiv ated by measurements of the cold dark matter. The search is harnessed on a Machine Learning approach\, which is adapted to different signal masses. I will scrutinize the observation of a 2.5 sigma excess of data versus the predicted SM background\, and briefly cover perspectives for this search.
END:VEVENT BEGIN:VEVENT SUMMARY:Dark matter searches at the LHC DTSTART:20231129T150000Z DTEND:20231129T170000Z DTSTAMP:20240329T082743Z UID:b9516597-c94b-4afe-9f2c-100fca6f6673 SEQUENCE:1 CREATED:20231127T153223Z DESCRIPTION:The lack of suitable dark matter (DM) particle candidates in t he Standard Model of particle physics (SM) hints at the need for a dark se ctor to be added to the model. One simplified dark matter model that does this type of extension is the DMsimp model. In this work\, we present a ph enomenological study where we successfully perform the reconstruction of t he top-anti-top system in the presence of a DM mediator\, Y0\, described b y the DMsimp model\, that couples to both the SM particles and the dark se ctor. Events involving Y0 production with a top-anti-top pair were generat ed for the Large Hadron Collider (LHC) using MadGraph5_aMC@NLO for four di fferent mediator masses: 0 GeV\, 1 GeV\, 10 GeV and 125 GeV. The reconstru ction of the top-anti-top system is done with a kinematic fit for the dile ptonic final states\, without reconstructing the mediator. Lastly\, confid ence level exclusion limits are set on the mediator couplings with the top quarks for all generated mediator masses using CP angular observables to probe the CP-nature of the couplings. LAST-MODIFIED:20231127T153223Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/dark-matter-searches-at-the-l hc/ X-ALT-DESC;FMTTYPE=text/html:The lack of suitabl
e dark matter (DM) particle candidates in the Standard Model of particle p
hysics (SM) hints at the need for a dark sector to be added to the model.
One simplified dark matter model that does this type of extension is the D
Msimp model.
In this work\, we present a phenomenological study
where we successfully perform the reconstruction of the top-anti-top syste
m in the presence of a DM mediator\, Y0\, described by the DMsimp model\,
that couples to both the SM particles and the dark sector. Events involvin
g Y0 production with a top-anti-top pair were generated for the Large Hadr
on Collider (LHC) using MadGraph5_aMC@NLO for four different mediator mass
es: 0 GeV\, 1 GeV\, 10 GeV and 125 GeV.
The reconstruction of th
e top-anti-top system is done with a kinematic fit for the dileptonic fina
l states\, without reconstructing the mediator. Lastly\, confidence level
exclusion limits are set on the mediator couplings with the top quarks for
all generated mediator masses using CP angular observables to probe the C
P-nature of the couplings.
O Large Hadron C
ollider (LHC)\, na Organização Europeia para a Investigação Nuclea
r (CERN)\, acelera principalmente feixes de protões uns contra os outros
com o objetivo de testar modelos e teorias na Física Fundamental. Espera-
se que comece a operar no regime de Alta Luminosidade (HL-LHC) no início
de 2029. O HL-LHC irá permitir um aumento substancial do número de colis
ões de interesse\, contribuindo para o estudo de um tipo ainda mais amplo
de eventos. No entanto\, a sobreposição de eventos indesejados\, fenóm
eno chamado de Pileup\, e muitos outros desafios tornarão a tarefa
de reconstrução de eventos\, especificamente o agrupamento de partícul
as em jatos (jet clustering)\, muito mais árdua.
Desta forma\, é urgente melhorar os algoritmos atua
is utilizados para a reconstrução de eventos e agrupamento de jatos ou d
esenvolver versões mais rápidas e eficientes. O foco desta Tese reside n
a exploração versões mais robustas e rápidas do K-Means\, com
ênfase numa implementação alternativa de uma sub-rotina quântica para
o cálculo de distâncias euclidianas com base no procedimento de Swap
Test. Propomos também uma aplicação mais flexível do K-Means\, que descarta jatos com baixo momento transversal\, de forma a que o n
úmero de jatos encontrados possa ser 0 e não 2\, como o algoritmo regula
r do K-Means exigiria. São ainda abordadas algumas limitações do
K-Means e exploramos a aplicabilidade do algoritmo quântico de Affinity Propagation para o problema do agrupamento de jatos. Finalme
nte\, para lidar com o Pileup\, fornecemos\, até onde sabemos\, a
primeira incorporação de um algoritmo de mitigação de Pileup co
m o K-Means.
O desempenho do s nossos algoritmos é testado em comparação com referências clássicas \, em particular algoritmos de recomposição sequencial\, como o kt e o A nti-kt. Com a rotina quântica proposta e os cortes aplicados\, os nossos algoritmos alcançaram uma melhor identificação de clusters e altas efic iências. Mostramos que a nossa implementação do K-Means é mais robusta e rápida\, uma vez que a sub-rotina quântica proposta requer mui to menos consultas do que o procedimento comum e calcula uma estimativa ma is precisa da distância euclidiana.
END:VEVENT BEGIN:VEVENT SUMMARY:Quantum Field Theory and Relativistic Stars DTSTART:20231130T143000Z DTEND:20231130T160000Z DTSTAMP:20240329T082743Z UID:48ebb1e0-8aab-47cd-99f9-aa781c62e275 SEQUENCE:1 CREATED:20231124T155851Z DESCRIPTION: ABSTRACT: What are the essential aspects of quantum theory ne eded in order to understand compact relativistic objects? Relying solely o n universal properties of QFTs at high energies\, we show that as a star c ontracts towards its Buchdahl (rather than its Schwarzschild) radius\, the effects of the trace anomaly become macroscopic at densities much below t he Planck scale. The consequences of this may be observable\, as we illust rate with minimally coupled scalar waves. LAST-MODIFIED:20231124T155851Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/quantum-field-theory-and-rela tivistic-stars/ X-ALT-DESC;FMTTYPE=text/html:ABSTRACT: What are the essential aspects of quantum theory needed in order to understand com pact relativistic objects? Relying solely on universal properties of QFTs at high energies\, we show that as a star contracts towards its Buchdahl ( rather than its Schwarzschild) radius\, the effects of the trace anomaly b ecome macroscopic at densities much below the Planck scale. The consequenc es of this may be observable\, as we illustrate with minimally coupled sca lar waves.
END:VEVENT BEGIN:VEVENT SUMMARY:Stability of spin-liquid phases against environment-induced dissip ation DTSTART:20231130T160000Z DTEND:20231130T180000Z DTSTAMP:20240329T082743Z UID:21b88013-2089-4148-91f3-edb7eff9bc45 SEQUENCE:2 CREATED:20231128T092259Z DESCRIPTION:É de grande interesse compreender o impacto do acoplamento de fases líquidas quânticas a diferentes ambientes. Neste trabalho\, estud amos a estabilidade da fase líquida de Luttinger relativamente a dissipa ção induzida pelo ambiente. Para concretizar este objetivo\, desenvolvem os um método de Monte Carlo quântico no formalismo de integral de caminh o em tempo contínuo com updates de Worm. As recentemente desenvolvidas wo rmhole updates\, que permitem a simulação eficiente de sistemas quântic os abertos\, foram adaptadas ao nosso método. Mostramos a validade da nos sa técnica testando-a em relação aos resultados do modelo de spin-bosã o provenientes de simulações de Monte Carlo quântico anteriores. També m comparamos os nossos resultados para o modelo de Bose-Hubbard dissipativ o de um e dois sítios relativamente a diagonalização exata. Estudamos\, então\, o modelo unidimensional de Bose-Hubbard num contexto não dissip ativo e dissipativo. No caso dissipativo\, o sistema é acoplado a um banh o de osciladores de tal forma que o sistema e o banho podem trocar energia e partículas\, mas o número total de bosões é conservado. Descobrimos que a fase líquida de Luttinger é instável para qualquer acoplamento i nfinitesimal a um banho ôhmico\, o que induz\, no seu lugar\, uma fase su perfluida ordenada onde a simetria U(1) é quebrada espontaneamente. Estes resultados são também apoiados por um argumento de contagem de potênci as. A fase de Mott permanece uma fase distinta para pequeno acoplamento ao banho\, mas adquire uma compressibilidade divergente no limite termodinâ mico. Para um acoplamento ao banho mais forte\, observamos uma transição de fase quântica desta fase para a fase superfluída ordenada. LAST-MODIFIED:20231128T092725Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/stability-of-spin-liquid-phas es-against-environment-induced-dissipation/ X-ALT-DESC;FMTTYPE=text/html:É de grande intere
sse compreender o impacto do acoplamento de fases líquidas quânticas a d
iferentes ambientes. Neste trabalho\, estudamos a estabilidade da fase lí
quida de Luttinger relativamente a dissipação induzida pelo ambiente. Pa
ra concretizar este objetivo\, desenvolvemos um método de Monte Carlo qu
ântico no formalismo de integral de caminho em tempo contínuo com update
s de Worm.
As recentemente desenvolvidas wormhole updates\, que
permitem a simulação eficiente de sistemas quânticos abertos\, foram ad
aptadas ao nosso método. Mostramos a validade da nossa técnica testando-
a em relação aos resultados do modelo de spin-bosão provenientes de sim
ulações de Monte Carlo quântico anteriores.
Também comparamo
s os nossos resultados para o modelo de Bose-Hubbard dissipativo de um e d
ois sítios relativamente a diagonalização exata. Estudamos\, então\, o
modelo unidimensional de Bose-Hubbard num contexto não dissipativo e dis
sipativo. No caso dissipativo\, o sistema é acoplado a um banho de oscila
dores de tal forma que o sistema e o banho podem trocar energia e partícu
las\, mas o número total de bosões é conservado.
Descobrimos
que a fase líquida de Luttinger é instável para qualquer acoplamento in
finitesimal a um banho ôhmico\, o que induz\, no seu lugar\, uma fase sup
erfluida ordenada onde a simetria U(1) é quebrada espontaneamente. Estes
resultados são também apoiados por um argumento de contagem de potência
s. A fase de Mott permanece uma fase distinta para pequeno acoplamento ao
banho\, mas adquire uma compressibilidade divergente no limite termodinâm
ico. Para um acoplamento ao banho mais forte\, observamos uma transição
de fase quântica desta fase para a fase superfluída ordenada.
Biossensores são d
ispositivos capazes de identificar ocorrências biológicas numa amostra\,
convertendo um sinal resultante num sinal elétrico que pode ser quantifi
cado. Em particular\, os fotodetetores de silício amorfo hidrogenado (a-S
i:H) são pertinentes para integração numa plataforma lab-on-a-chip proj
etada para deteção optoelectrónica.
Este trabalho teve como f
oco o desenvolvimento de um novo fotodetector de a-Si:H com base numa jun
ção p-i-n lateral\, para aplicações posteriores de biodeteção. Esta
estrutura contrasta com o fotodíodo padrão\, que é composto por uma jun
ção p-i-n perpendicular. A microfabricação do dispositivo foi realizad
a em ambiente de sala limpa e foi alcançado um processo otimizado após d
uas gerações de dispositivos.
O novo dispositivo foi caracteri
zado quanto às suas principais características: fotocorrente e corrente
negra-tensão\, com menção dos mecanismos de condução no escuro\; efic
iência quântica externa em função do comprimento de onda incidente\; e
fotocorrente em funcão do fluxo de fotões. Foi observada retificação
nestes dispositivos\, apesar de tenderem para a atuação como um fotodío
do sob polarização reversa e como um detetor fotocondutor sob polarizaç
ão direta.
Implantação ióni
ca permite dopagem de GaN em concentrações elevadas para fabrico de disp
ositivos com base em GaN pre-depositado\, mas cria defeitos. Espectrometri
a de Retrodispersão de Rutherford com Canalização (RBS/C) permite o est
udo destes defeitos\, mas isto é dificultado pela diversidade destes.
Simulações Monte Carlo (McChasy) e A
proximação de Dois Feixes (TBA) foram comparadas em análise de espectro
s de RBS/C de c-\, m- e a-GaN implantado com Ar. Os perfis obtidos foram c
omparados com imagens de Microscopia eletrónica de Transmissão (TEM) e c
ontextualizados com o modelo de Hecking.
RBS/C mostra perfis de Átomos Aleatoriamente Dispersos (RDA) relati
vamente semelhantes para c- e m-GaN\, com a-GaN apresentanto muito menos d
anos. Estas curvas mostram crescimento até saturar para fluências de Ar
entre 1015 e 1016 at/cm2\, seguido de crescimento de defeitos atribuído a
amorfização. Os modelos obtiveram perfis semelhantes\, com McChasy apre
sentando valores consistentemente inferiores a baixa (<\; 250 nm) profun
didade e superiores caso contrário. Defeitos extensos foram modelados com
o loops de deslocações seguindo uma distribuição de vagas\, com compor
tamento semelhante a RDA até aproximadamente 1016 at/cm2\, divergindo de
saturação para fluências superiores.
Comparando estes resultados com imagens de TEM\, os perfis de RDA com fluências de 8x1015 at/cm2 eram semelhantes entre modelos mas ambos subes timam ligeiramente a profundidade dos danos. Defeitos extensos consistem m aioritariamente de falhas de empilhamento (tanto basais como prismáticas) para c- e m-GaN\, e loops de deslocações para a-GaN. Para fluências de 4x1016 at/cm2\, os perfis de danos não coincidiam com experiência devid o à presença de bolhas de Ar e amorfização.
END:VEVENT BEGIN:VEVENT SUMMARY:Amazônia e a Atual Política Ambiental Brasileira: IST Distinguis hed Lecture (Joint organization with Plataforma de Ciências e Engenharia do Ambiente do IST) DTSTART:20231204T150000Z DTEND:20231204T160000Z DTSTAMP:20240329T082743Z UID:5c085456-1c80-4c86-86ce-9ed2e35b4f0f SEQUENCE:2 CREATED:20231109T102952Z DESCRIPTION:ResumoDesde o final da década de 1980\, o Brasil teve grande protagonismo na questão de mudanças climáticas e combate à degradaçã o ambiental. Um exemplo paradigmático dessa política de estado é o proj eto PRODES\, do Instituto Nacional de Pesquisas Espaciais\, que faz o moni toramento por satélite do desmatamento por corte raso na Amazônia Legal\ , fornecendo\, desde 1988\, as correspondentes taxas anuais. Seus dados s ão internacionalmente considerados entre as melhores series temporais de monitoramento de desmatamento em florestas tropicais. Infelizmente\, duran te o período de 2019 a 2022\, o Governo Federal adoptou uma política neg acionista com relação ao aquecimento global e à preservação ambiental \, estimulando o desmatamento da Amazônia\, que cresceu de 5.078 Km2\, em 2018\, a 10.573 km2\, em 2022. Esse aumento do desmatamento fez com que boa parte da Floresta Amazônica passasse de absorvedor para emissor de g ás carbônico para a atmosfera. Essa política predatória foi felizmente revertida com a posse do novo Governo em janeiro de 2023. Entre janeiro e agosto deste ano\, houve uma redução de cerca de 48% do desmatamento na Amazônia Legal\, em comparação com o mesmo período do ano passado. Ne ste colóquio farei uma breve descrição das diferentes ações do atual Governo com relação ao desenvolvimento sustentável e combate à degrada ção ambiental no Brasil\, incluindo estímulo a projetos científicos di rigidos a esses tópicos. LAST-MODIFIED:20231130T141319Z LOCATION:Anfiteatro Abreu Faro - Complexo Interdisciplinar URL:http://df.vps.tecnico.ulisboa.pt/eventos/amaz%C3%B4nia-e-a-atual-pol%C 3%ADtica-ambiental-brasileira/ X-ALT-DESC;FMTTYPE=text/html:Resumo
D
esde o final da década de 1980\, o Brasil teve grande protagonismo na que
stão de mudanças climáticas e combate à degradação ambiental. Um exe
mplo paradigmático dessa política de estado é o projeto PRODES\, do Ins
tituto Nacional de Pesquisas Espaciais\, que faz o monitoramento por saté
lite do desmatamento por corte raso na Amazônia Legal\, fornecendo\, desd
e 1988\, as correspondentes taxas anuais.
Seus dados são intern
acionalmente considerados entre as melhores series temporais de monitorame
nto de desmatamento em florestas tropicais. Infelizmente\, durante o perí
odo de 2019 a 2022\, o Governo Federal adoptou uma política negacionista
com relação ao aquecimento global e à preservação ambiental\, estimul
ando o desmatamento da Amazônia\, que cresceu de 5.078 Km2\, em 2018\, a
10.573 km2\, em 2022.
Esse aumento do desmatamento fez com que
boa parte da Floresta Amazônica passasse de absorvedor para emissor de g
ás carbônico para a atmosfera. Essa política predatória foi felizmente
revertida com a posse do novo Governo em janeiro de 2023. Entre janeiro e
agosto deste ano\, houve uma redução de cerca de 48% do desmatamento na
Amazônia Legal\, em comparação com o mesmo período do ano passado. Ne
ste colóquio farei uma breve descrição das diferentes ações do atual
Governo com relação ao desenvolvimento sustentável e combate à degrada
ção ambiental no Brasil\, incluindo estímulo a projetos científicos di
rigidos a esses tópicos.
O sistema de diagn
óstico magnético fornece dados fundamentais para a operação e explora
ção científica de dispositivos de fusão nuclear por confinamento magn
ético. Embora esteja em constante aperfeiçoamento desde os primeiros dis
positivos\, a construção de novos reatores representa uma oportunidade p
ara avanços em diagnósticos magnéticos\, adaptados aos desafios e oport
unidades específicos. O tokamak COMPASS-U\, desenvolvido em Praga\, na Re
pública Checa\, terá um conjunto único de parâmetros\, dos quais se de
staca o campo magnético toroidal de 5 T e a parede interna metálica aque
cida a altas temperaturas.
Graças a uma ampla coleção de sist
emas de diagnóstico\, este dispositivo estará numa posição de suportar
a operação do ITER e abordar problemas relevantes tanto para o DEMO com
o futuras centrais elétricas. Nesta tese\, os desafios relativos ao desen
volvimento de um sistema de diagnóstico magnético para uma máquina tão
única são discutidos e é exposto o projeto e desenvolvimento dos princ
ipais subsistemas: desde os sensores ao cabeamento e eletrónica.
São desenvolvidos métodos para calibração e medição precisas de se
nsores magnéticos\; estuda-se a mitigação da influência de estruturas
metálicas em sensores\; são tiradas conclusões sobre a escolha de cabos
de transmissão de dados para longas distâncias\; é qualificada a imple
mentação de métodos de integração numérica em tempo-real e novo hard
ware é desenvolvido.
Embora estas etapas de desenvolvimento ten
ham como objetivo último a adequação à operação e ao programa cient
ífico do COMPASS-U\, as abordagens sistemáticas descritas e levadas a ca
bo podem ser aplicadas a dispositivos futuros.
Digital twins were
born 20 years ago but have only now matured enough\, being strongly suppor
ted by the advancements of Industry 4.0. By integrating sensors\, internet
of things\, cloud computing\, and machine learning\, digital twins are en
dowed with strong capabilities of monitoring\, prediction\, and diagnosis.
This in turn assures a more efficient and optimized management
of power grids\, promoting\, amongst others services\, demand-response str
ategies\, renewable energy sources and prosumers integration in the grid\,
fault prediction\, and maintenance routines scheduling. Digital twins bri
ng integration and intelligence to operations management\, highly supporti
ng decision making. The path paved by this technology is just beginning. I
n the following years\, digital twins will further penetrate into differen
t industries and will soon become an essential tool in every control room.
The objective of this work will be to implement a digital twin of the energy consumption of Instituto Superi or Técnico. To achieve this\, robust forecasting models will be created\, supported by real-time data provided by the smart meters already installe d on campus. A framework will be designed to independently and automatical ly update the models as new data is collected\, ensuring they remain faith ful to the real process. The collected data and the resulting predictions will be integrated into a novel visualization tool permeated with importan t visual elements\, whose collective added value will ultimately support a better management of the electricity service in Instituto Superior Técni co.
END:VEVENT BEGIN:VEVENT SUMMARY:Accelerating track reconstruction using GPUs at ATLAS DTSTART:20231205T110000Z DTEND:20231205T130000Z DTSTAMP:20240329T082743Z UID:9c276833-6b8f-43d9-b6c3-2b7504f7d7a4 SEQUENCE:1 CREATED:20231130T093056Z DESCRIPTION:Nas últimas décadas\, os aceleradores de partículas foram c ruciais para grande parte avanços experimentais no ramo da ciência que e studa os constituintes fundamentais do universo\, a física de partículas . O atual entendimento teórico\, o Modelo Padrão\, tem lacunas cuja reso lução requer a utilização de conjuntos de dados cada vez maiores\, per mitindo a observação de processos raros ainda por estudar. Por este moti vo\, o LHC beneficiará de um projeto de modernização que visa aumentar significativamente a taxa de colisões\, o LHC de Alta Luminosidade (HL-LH C). Nas várias experiências\, tal como ATLAS\, é imperativo melhorar as capacidades computacionais para lidar com o elevado fluxo de dados. Uma a lternativa emergente é a utilização de GPUs como plataformas auxiliares para as quais parte da carga de trabalho é delegada. Estes dispositivos potenciam a velocidade das aplicações através de processamento paralelo massivo.O trabalho apresentado nesta tese procura desenvolver e melhorar algoritmos de reconstrução de trajectórias de partículas recorrendo a GPUs. A reconstrução é um processo crucial que consiste em identificar o percurso de cada partícula ao atravessar o detetor e interagir com mate rial sensível\, permitindo o estudo das suas características. Em ATLAS\, é a tarefa que exige maior tempo computacional. A cadeia de reconstruç ão do pacote ACTS foi parcialmente implementada com sucesso utilizando CU DA e SYCL: desde dados que provêm diretamente do detetor\, correspondente s a células ativas\, até à produção de estimativas iniciais de trajec tos de partículas.O estudo do desempenho apresentado nesta tese revelou r esultados promissores: a capacidade de processamento para eventos simulado s em condições semelhantes às que se esperam para o HL-LHC foi aumentad a até 5 vezes quando comparada com a utilização total de um CPU topo de gama. LAST-MODIFIED:20231130T093056Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/accelerating-track-reconstruc tion-using-gpus-at-atlas/ X-ALT-DESC;FMTTYPE=text/html:Nas últimas décad
as\, os aceleradores de partículas foram cruciais para grande parte avan
ços experimentais no ramo da ciência que estuda os constituintes fundame
ntais do universo\, a física de partículas. O atual entendimento teóric
o\, o Modelo Padrão\, tem lacunas cuja resolução requer a utilização
de conjuntos de dados cada vez maiores\, permitindo a observação de proc
essos raros ainda por estudar.
Por este motivo\, o LHC beneficia
rá de um projeto de modernização que visa aumentar significativamente a
taxa de colisões\, o LHC de Alta Luminosidade (HL-LHC). Nas várias expe
riências\, tal como ATLAS\, é imperativo melhorar as capacidades computa
cionais para lidar com o elevado fluxo de dados. Uma alternativa emergente
é a utilização de GPUs como plataformas auxiliares para as quais parte
da carga de trabalho é delegada. Estes dispositivos potenciam a velocida
de das aplicações através de processamento paralelo massivo.
<
/p>
O trabalho apresentado nesta tese procura des
envolver e melhorar algoritmos de reconstrução de trajectórias de part
ículas recorrendo a GPUs. A reconstrução é um processo crucial que con
siste em identificar o percurso de cada partícula ao atravessar o detetor
e interagir com material sensível\, permitindo o estudo das suas caracte
rísticas. Em ATLAS\, é a tarefa que exige maior tempo computacional. A c
adeia de reconstrução do pacote ACTS foi parcialmente implementada com s
ucesso utilizando CUDA e SYCL: desde dados que provêm diretamente do dete
tor\, correspondentes a células ativas\, até à produção de estimativa
s iniciais de trajectos de partículas.
O estudo do desempenho ap
resentado nesta tese revelou resultados promissores: a capacidade de proce
ssamento para eventos simulados em condições semelhantes às que se espe
ram para o HL-LHC foi aumentada até 5 vezes quando comparada com a utiliz
ação total de um CPU topo de gama.
Neste documento tra
ta-se o problema do valor inicial (PVI) em Relatividade Geral (RG)\, bem c
omo algumas das suas aplicações. São discutidos alguns formalismos mate
máticos necessários - folheações\, resultados sobre equações diferen
ciais parciais em espaços tempos curvos\, e spinors. Com estas ferramenta
s\, esboçam-se os traços gerais do PVI e alguns dos principais resultado
s na área\, tais como o teorema de Choquet-Bruhat para a existência e un
icidade de desenvolvimentos de Einstein em vácuo e o subsequente enfraque
cimento das condições de regularidade dos dados iniciais\, feito por Pla
nchon e Rodnianski.
Segue-se uma discussão acerca da estrutura
causal destes desenvolvimentos de Einstein\, bem como da inclusão de mat
éria através do tensor de energia-momento e de torção na conexão\, ge
neralizando-se resultados disponíveis na literatura. Passa-se de seguida
ao estudo da questão da conservação de simetria de Killing no desenvolv
imento de dados iniciais\, obtendo-se uma equação de propagação hiperb
ólica e não-homogénea para a derivada de Lie da métrica enquanto quant
idade zero.
Analisa-se o termo não-homogéneo em pormenor - uma
colineação do tensor de Ricci - e apresentam-se dois exemplos de campos
de matéria\, um dos quais admite conservação da simetria com condiçõ
es relativamente fracas - o campo escalar massivo de Klein-Gordon - e outr
o - o campo eletromagnético - que requer restrições mais fortes para ga
rantir preservação da simetria.
Termina-se discutindo um tópi
co semelhante: o problema de valor inicial para twistors\, spinors
de Killing. Estuda-se a propagação da chamada equação dos twistors em
variedades planas\, usada para obter uma caracterizar espaços-tempos de M
inkowski e de ondas planas ao nível das condições iniciais.
Os sensores de magn
etorresistência anisotrópica são fundamentais em várias aplicações d
evido ao seu baixo consumo de energia\, escalabilidade e rentabilidade. Co
ntudo\, esta tecnologia estagnou nos últimos anos\, sendo necessário exp
lorar caminhos alternativos para a sua otimização.
Este estudo
focou-se na otimização de sensores AMR de permalloy Ni0.8Fe0.2 para apl
icações de posicionamento\, atualmente em produção no INESC MN\, atrav
és de diversas técnicas. A avaliação da transição do sistema N3000 p
ara o N3600\, que tem um potencial de aumento no rendimento de 78%\, revel
ou características semelhantes entre as amostras\, validando então esta
mudança. A inclusão de uma camada de buffer de Ta melhorou as pro
priedades cristalinas\, mas levou a uma diminuição do AMR.
Con
trariamente\, em amostras sem buffer\,annealing magnético m
elhorou as propriedades cristalinas e magnéticas\, especialmente em tempe
raturas mais baixas. Valores de AMR de 2\,24% e 2\,29% foram atingidos\, p
ermitindo estabelecer uma correlação entre o crescimento do grão e o au
mento deste parâmetro. Camadas de dusting de Pt\, sem annealing
\, melhoraram o valor de AMR de 2.04\\% para 2\,20\\%\, enquanto as de
MgO resultaram numa diminuição. Após\, amostras com Pt mostraram resis
tividade aumentada e AMR mais baixo.
Em contraste\, camadas de M
gO com t>\;1nm mostraram-se promissoras na otimização do desempenho do
s sensores\, atingindo valores de AMR até 2\,49% após 5h a 370⁰C. À l
uz dos resultados\, a incorporação de camadas de dusting de Pt e
MgO surge como uma via promissora para adaptar o comportamento e desempenh
o dos sensores AMR\, abrindo caminho para futuras inovações no campo da
tecnologia de dispositivos magnéticos.
Uma estação de de
teção de superfície (SD) no Observatório Pierre Auger equipada tanto c
om MARTA (Muon Array with RPCs for Tagging Air showers) como com um deteto
r de cintilação de superfície (SSD) oferece a oportunidade de realizar
novos tipos de medições de raios cósmicos a altas energias. Este trabal
ho explora a possibilidade de utilizar uma estação que se encontre nesta
s condições para realizar uma medição da distribuição de energia das
partículas de cascatas atmosféricas (EAS)\, para as componentes eletrom
agnéticas e muónicas da cascata.
Neste trabalho é desenvolvido um método que permite modificar a distribu
ição de energia original obtida a partir das simulações e utilizá-la
para testar a sensibilidade dos detetores. Aqui demonstra-se que tanto o S
D quanto o detetor de RPC (acrónimo para Resistive Plate Chambers) são s
ensíveis a modificações na região de altas energias da distribuição
eletromagnética\, especialmente em casos em que a estação se encontra p
róxima do centro da cascata.
Por outro lado\, o SSD é insensí
vel à modificação desde que a modificação conserve o número total de
partículas na distribuição. Os resultados para a distribuição de mu
ões são\, no entanto\, inconclusivos. Em regiões distantes do centro da
cascata\, o baixo nível estatístico das distribuições de muões é pr
eocupante\, uma vez que pode estar a afetar a qualidade da modificação d
o espectro. A análise aqui realizada é idealizada em função da estaç
ão Peter Mazur localizada no Observatório Pierre Auger\, pois é atualme
nte a única estação equipada com o MARTA.
Resumo
Interações fotão-fotão no vácuo têm uma secção efi
caz desprezável\, em regimes de baixas energias. No entanto\, na presenç
a de um meio não-linear desfocalizante do tipo Kerr\, como um vapor quent
e de rubídio\, ou de outro metal alcalino\, o campo de polarização elé
trica atua como um mediador de interações\, assumindo um papel important
e nestes sistemas. O comportamento coletivo entre fotões é previsto atra
vés de uma formulação hidrodinâmica\, justificando a designação de f
luidos quânticos de luz.
Devido às semelhanças entre a equaç
ão não-linear de Helmholtz e a equação de Gross-Pitaevskii\, bem conhe
cida na teoria de condensação de Bose-Einstein\, prevê-se que os fluido
s quânticos de luz sejam bons simuladores de condensados de Bose-Einstein
\, funcionando a altas temperaturas\, sendo assim uma opção mais barata
e menos complexa na sua construção e manutenção. Apesar da semelhança
formal\, é importante salientar as suas diferenças\, sendo estas aqui t
ambém exploradas.
A configuração experimental de uma experiê
ncia de fluidos quânticos de luz é detalhada\, começando pela estrutura
atómica do rubídio até todos os diferentes componentes para o controlo
dos parâmetros relevantes\, nomeadamente a unidade de controlo de temper
atura que surge para controlar a densidade do vapor. A dinâmica de uma im
pureza num condensado de Bose-Einstein foi estudada na presença de ruído
quântico. Os resultados simulados numericamente para uma impureza tipo v
órtice são discutidos com as condições necessárias para conduzir um m
ovimento superdifusivo.
O estudo do Plasma
de Quarks e Gluões (QGP)\, a fase desconfinada da Cromodinâmica Quânti
ca (QCD)\, constitui atualmente uma área de investigação muito ativa e
em rápido desenvolvimento. O QGP é a fase do Universo no seu primeiro mi
crossegundo de existência\, podendo também ser formado em colisões de i
ões pesados ultrarelativistas.
Nessas experiências\, jatos - s
prays colimados de hadrões - podem ser formados\, constituindo uma ferram
enta crucial para estudar o QGP\, feito por análise das suas modificaçõ
es ao viajar pelo plasma\, por sua vez conseguido através da comparação
com jatos em colisões Protão-Protão\, que evoluem no vácuo.
Uma das principais manifestações da inter
ação dos jatos com o QGP é uma perda de energia significativa. Outra ma
nifestação crucial é chamada de resposta do meio\, constituindo um acr
éscimo de partículas decorrentes do QGP\, que são reconstruídas dentro
do jato final.
Neste trabalho\, f unções de correlação de energia\, uma nova classe de observáveis\, fo ram calculadas para jatos em colisões de iões pesados e analisadas. As f unções de correlação evidenciaram as diferentes fases da QCD pelos qua is os constituintes dos jatos passam\, e a análise de modificações desp rezando a resposta do meio apresentou um comportamento compatível com a i deia de que jatos que evoluem no QGP hadronizam numa escala de tempo poste rior à de jatos que evoluem no vácuo. Essas funções de correlação ta mbém se mostraram sensíveis à resposta do meio\, com sensibilidades dif erentes considerando diferentes versões da função.
END:VEVENT BEGIN:VEVENT SUMMARY:Equipartition and Entanglement - Relation between ergodicity measu res DTSTART:20231206T143000Z DTEND:20231206T160000Z DTSTAMP:20240329T082743Z UID:ae1d2975-62ea-4a79-875d-76bf456da7cc SEQUENCE:1 CREATED:20231205T142543Z DESCRIPTION:Similarly to the ergodicity hypothesis in classical chaotic sy stems\, in the quantum setting there is asimilar concept\, related to quan tum thermalization and equipartition over degrees of freedom anddubbed as the eigenstate thermalization hypothesis. This concept is very useful as i t provides a linkbetween classical and quantum chaos. The concept of multi fractality of quantum wave-functions is away to break the above ergodicity in terms of chaotization and equipartitioning over degrees offreedom in q uantum systems. On the other hand\, in quantum information theory it is th e entanglemententropy which represents the main measure of ergodicity and thermalization. On the third side\, in theeigenstate thermalization hypoth esis the fluctuations of local observables and their scaling with thesyste m size play the central role. In this talk I will represent an exact relat ion between the above threemeasures\, namely multifractal dimensions\, sca ling of fluctuations of local observables and the (Renyi)entanglement entr opy. I will show that the fractal dimension of the non-ergodic wave functi on puts anupper bound on its entanglement entropy [1]. I will also provide a couple of explicit examplesdemonstrating that the entanglement entropy may reach its ergodic (Page) value when the wavefunction is still highly n on-ergodic and occupies a zero fraction of the total Hilbert space. If tim e permitsI will briefly discuss some other possible deviations from ergodi city relevant for the chaotic many-body. LAST-MODIFIED:20231205T142543Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/equipartition-and-entanglemen t-relation-between-ergodicity-measures/ X-ALT-DESC;FMTTYPE=text/html:Similarly to the er godicity hypothesis in classical chaotic systems\, in the quantum setting there is asimilar concept\, related to quantum thermalization and equipart ition over degrees of freedom anddubbed as the eigenstate thermalization h ypothesis. This concept is very useful as it provides a linkbetween classi cal and quantum chaos. The concept of multifractality of quantum wave-func tions is away to break the above ergodicity in terms of chaotization and e quipartitioning over degrees offreedom in quantum systems. On the other ha nd\, in quantum information theory it is the entanglemententropy which rep resents the main measure of ergodicity and thermalization. On the third si de\, in theeigenstate thermalization hypothesis the fluctuations of local observables and their scaling with thesystem size play the central role. I n this talk I will represent an exact relation between the above threemeas ures\, namely multifractal dimensions\, scaling of fluctuations of local o bservables and the (Renyi)entanglement entropy. I will show that the fract al dimension of the non-ergodic wave function puts anupper bound on its en tanglement entropy [1]. I will also provide a couple of explicit examplesd emonstrating that the entanglement entropy may reach its ergodic (Page) va lue when the wavefunction is still highly non-ergodic and occupies a zero fraction of the total Hilbert space. If time permitsI will briefly discuss some other possible deviations from ergodicity relevant for the chaotic m any-body.
END:VEVENT BEGIN:VEVENT SUMMARY:Energetics of Trapped-Ion Quantum Computation DTSTART:20231206T170000Z DTEND:20231206T190000Z DTSTAMP:20240329T082743Z UID:d7532250-04af-42c8-895d-61d84b030b6d SEQUENCE:2 CREATED:20231205T085942Z DESCRIPTION:A computação quântica recorre a fenómenos da mecânica qu ântica para resolver problemas demasiado complexos para os computadores c lássicos. O entusiasmo em torno das suas potenciais aplicações tem leva do a um investimento crescente de recursos para o desenvolvimento de compu tadores quânticos escaláveis com desempenhos temporais cada vez melhores . A questão da eficiência energética dos computadores quânticos\, no e ntanto\, apenas ganhou alguma atenção recentemente. Ainda está em falta uma compreensão exacta dos recursos necessários para operar um computad or quântico com o desempenho computacional pretendido e da forma como os requisitos energéticos podem afetar a escalabilidade. Nesta tese\, foi es tudada uma implementação do algoritmo para a transformada de Fourier qu ântica numa plataforma de iões confinados. O principal objetivo foi a ob tenção de uma caracterização teórica dos custos energéticos da compu tação quântica\, investigando o consumo de energia dos diferentes eleme ntos de um computador quântico de iões confinados. O algoritmo foi simul ado e\, incluindo diferentes modelos de ruído na simulação\, o seu dese mpenho na presença de ruído quântico foi analisado. O custo energético da experiência foi estimado através da análise dos seus diferentes com ponentes e das etapas envolvidas numa computação quântica\, desde o arr efecimento e preparação dos iões até à implementação do algoritmo e medição do resultado. Um potencial dimensionamento dos custos energéti cos foi discutido e utilizado para procurar um possível limiar para uma v antagem energética quântica sobre os supercomputadores clássicos. LAST-MODIFIED:20231205T090103Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/energetics-of-trapped-ion-qua ntum-computation/ X-ALT-DESC;FMTTYPE=text/html:A computação quâ
ntica recorre a fenómenos da mecânica quântica para resolver problemas
demasiado complexos para os computadores clássicos. O entusiasmo em torno
das suas potenciais aplicações tem levado a um investimento crescente d
e recursos para o desenvolvimento de computadores quânticos escaláveis c
om desempenhos temporais cada vez melhores.
A questão da efici
ência energética dos computadores quânticos\, no entanto\, apenas ganho
u alguma atenção recentemente. Ainda está em falta uma compreensão exa
cta dos recursos necessários para operar um computador quântico com o de
sempenho computacional pretendido e da forma como os requisitos energétic
os podem afetar a escalabilidade.
Nesta tese\, foi estudada uma implementação do algoritmo para a transfor
mada de Fourier quântica numa plataforma de iões confinados. O principal
objetivo foi a obtenção de uma caracterização teórica dos custos ene
rgéticos da computação quântica\, investigando o consumo de energia do
s diferentes elementos de um computador quântico de iões confinados.
O algoritmo foi simulado e\, incluindo diferentes modelos de ruído
na simulação\, o seu desempenho na presença de ruído quântico foi an
alisado. O custo energético da experiência foi estimado através da aná
lise dos seus diferentes componentes e das etapas envolvidas numa computa
ção quântica\, desde o arrefecimento e preparação dos iões até à i
mplementação do algoritmo e medição do resultado. Um potencial dimensi
onamento dos custos energéticos foi discutido e utilizado para procurar u
m possível limiar para uma vantagem energética quântica sobre os superc
omputadores clássicos.
A radioterapia é
um tipo de tratamento do cancro essencial\, cuja eficiência pode ser melh
orada com o uso de radiosensibilizadores. Estes compostos são administrad
os em simultâneo com radiação ionizante\, aumentando assim a sensibilid
ade das células aos efeitos nocivos da radiação. Por essa razão\, inve
stigar radiossensibilizadores é fulcral para otimizar o tratamento de can
cro.
A presente tese avaliou a capacidade de dois novos composto
s\, PDS-pz e Re-PDS-pz - ligandos G-quadrúplex (G4) sintetizados no C2TN
- de se comportarem como radiossensibilizadores\, em células do cancro da
próstata (na linha celular PC3). Este possível comportamento foi estuda
do através de ensaios experimentais biológicos e radiobiológicos e de s
imulações de Monte Carlo. Os efeitos dos compostos PDS-pz e Re-PDS-pz fo
ram comparados aos do composto comercial e conhecido radiossensibilizador
RHPS4. As células analisadas foram irradiadas\, em diferentes estudos\, c
om raios gama de cobalto-60 em doses de 0\,5 Gy a 6 Gy.
Os ensai
os experimentais demonstram aumento da citotoxicidade nas células aquando
da administração dos compostos estudados e maior efeito nocivo aquando
da atuação simultânea destes com a radiação - o que confirma o compor
tamento radiosensibilizador do PDS-pz e do Re-PDS-pz. O trabalho computaci
onal foi elaborado com sucesso\, que validou o débito de dose de 1 Gy/min
\, emitido pelo irradiador Precisa-22\, e descreveu o comportamento tempor
al das espécies reativas de oxigénio (ROS) criadas após irradiação.
p>
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bridging the gap between modeling and experiments in low temperatu
re plasmas
DTSTART:20231207T110000Z
DTEND:20231207T130000Z
DTSTAMP:20240329T082743Z
UID:fa932d60-75d3-4609-8381-cf70b26fd0f9
SEQUENCE:1
CREATED:20231130T154424Z
DESCRIPTION:Abstract: Low-temperature plasma (LTP) science and technology
have become integral to numerous applications with far-reaching implicatio
ns for our society. From advancing microelectronics industry through plasm
a–surface interactions and microprocessor fabrication to enabling electr
ic propulsion systems for satellite motion control\, LTPs play a pivotal r
ole in diverse fields. The continuous evolution of LTPs has given rise to
novel application areas\, including multidisciplinary research domains suc
h as plasma agriculture\, plasma catalysis and plasma-based gas reforming.
Despite these advancements\, understanding and controlling non-equilibriu
m plasma processes remain challenging due to the need to identify key phen
omena operating across spatial and temporal scales spanning several orders
of magnitude.This seminar will explore ongoing efforts dedicated to under
standing the key role played by parameters of relevance (electric field\,
vibrational excitation\, gas heating\, etc.) in LTPs. The presentation wil
l be particularly focused on plasma-based applications targeted at convert
ing pollutant gases into value-added products\, offering sustainable alter
natives to fossil fuels\, thereby contributing to the decarbonization of e
nergy systems. I will discuss past\, current and future activities aimed a
t advancing our understanding of LTPs by closing the gap between modeling
and experimental results. The talk will also underscore the challenges ass
ociated with establishing benchmark experiments for model validation and s
implifying complex plasma kinetic schemes.
LAST-MODIFIED:20231130T154424Z
LOCATION:Anfiteatro PA1\, Piso -1 - Pavilhão de Matemática\, Campus da
Alameda
URL:http://df.vps.tecnico.ulisboa.pt/eventos/bridging-the-gap-between-mode
ling-and-experiments-in-low-temperature-plasmas/
X-ALT-DESC;FMTTYPE=text/html:
Abstract: Lo
w-temperature plasma (LTP) science and technology have become integral to
numerous applications with far-reaching implications for our society. From
advancing microelectronics industry through plasma–surface interactions
and microprocessor fabrication to enabling electric propulsion systems fo
r satellite motion control\, LTPs play a pivotal role in diverse fields.
The continuous evolution of LTPs has given rise to novel applicat
ion areas\, including multidisciplinary research domains such as plasma ag
riculture\, plasma catalysis and plasma-based gas reforming. Despite these
advancements\, understanding and controlling non-equilibrium plasma proce
sses remain challenging due to the need to identify key phenomena operatin
g across spatial and temporal scales spanning several orders of magnitude.
This seminar will explore ongoing effor
ts dedicated to understanding the key role played by parameters of relevan
ce (electric field\, vibrational excitation\, gas heating\, etc.) in LTPs.
The presentation will be particularly focused on plasma-based application
s targeted at converting pollutant gases into value-added products\, offer
ing sustainable alternatives to fossil fuels\, thereby contributing to the
decarbonization of energy systems.
I will discuss past\, curren
t and future activities aimed at advancing our understanding of LTPs by cl
osing the gap between modeling and experimental results. The talk will als
o underscore the challenges associated with establishing benchmark experim
ents for model validation and simplifying complex plasma kinetic schemes.
Este trabalho explo
ra sensores túnel magnetoresistivos (TMR) que desempenham um papel fundam
ental em medições magnéticas devido ao seu alto desempenho\, consumo el
éctrico\, sensibilidade e capacidade de deteção de baixos campos magné
ticos\, com aplicações em medições magnéticas no espaço ou magnetofi
siologia.
No entanto\, necessitam de dispositivos capazes de det
etar campos magnéticos na ordem dos pT. Uma possível estratégia para g
arantir deteção destes campos magnéticos consiste em 3D packing
de sensores TMR\, que sobrepostos verticalmente em níveis completos\, per
mitem a obtenção de uma melhor detetividade.
Neste caso\, efei
tos de topografia passam a ter um papel relevante e diferentes estratégia
s foram introduzidas no design de sensores para avaliar o seu efeit
o. Um tratamento de feixe de iões de O2 foi estudado\, com o objetivo a a
umentar o rendimento do processo de fabricação de sensores. A redeposiç
ão metálica durante a definição do pilar leva a uma redução de MR\,
e\, por isso\, a uma menor sensibilidade. A estratégia desenvolvida pode
contribuir para a melhoria dos processos de fabricação no INESC MN.
ABSTRACT:
Effective field theory (EFT) provides a way of paramet
erizing strong-field deviations from General Relativity that might be obse
rvable in the gravitational waves emitted in a black hole merger. To perfo
rm numerical simulations of black hole mergers in an EFT\, it is necessary
that the theory admits a well-posed initial value formulation.
In the first part of my talk\, I will review recent results on the initial
value formulation of gravitational EFTs (beyond General Relativity) with
second-order equations of motion. In the second part\, I will discuss some
ideas to deal with EFTs with higher derivative equations.
As aplicações par
a sensores magnetoresistivos\, como junções de efeito túnel (JET)\, tê
m crescido constantemente\, com necessidade de maior resiliência térmica
e maior alcance de condições para aplicações na faixa de pico a milit
esla. O presente trabalho mostrou MnNi ser um candidato viável para um AF
M em bicamadas exchange coupled de sensores JET\, com a tecnologia IBAD su
perando os resultados da IBD\, maximizando o campo de exchange bias e a te
mperatura de blocking.
O trabalho r
ealizado no INESC MN permitiu a deposição\, medição e fabricação de
sensores JET. Estudos de espessura de bicamada foram realizados\, com melh
ores resultados alcançados para camadas espessas de MnNi (>\;40nm)\, e
IBAD permitiu uma melhoria de 160Oe para 1046Oe de exchange bias. Estudos
de temperatura de annealing mostraram melhores condições para 2h a 300°
C. A análise de AFM e XRD mostrou que IBAD reduz a rugosidade superficial
do AFM\, facilitando o correto crescimento cristalino das camadas superio
res\, com uma diminuição simultânea de 16\\% no tamanho do grão. Tb de
300°C~310°C foi encontrado para bicamadas MnNi-IBAD\, e Tb de 424°C pa
ra IBD. Fenómenos incomuns como um aumento inicial em Hex com a temperatu
ra e uma diminuição acentuada de Hex perto de Tb foram observados.
<
br/>
Sensores JET microfabricados foram carac terizados com equipamentos VSM e R(H). Uma diminuição efetiva do exchang e bias foi observada para amostras IBAD\, e em ambas as amostras nenhuma a nisotropia de forma cruzada foi alcançada\, com a camada de referência n ão definida. Foi observado um deslocamento da curva R(H)\, sensores funci onais foram mapeados e valores baixos de MR de 0.76% foram alcançados\, c om melhores resultados para pilares retangulares do que elípticos.
END:VEVENT BEGIN:VEVENT SUMMARY:Information Diffusion on Dynamic Networks DTSTART:20231207T160000Z DTEND:20231207T180000Z DTSTAMP:20240329T082743Z UID:b3539cb6-1a3b-499a-a01e-8c65634551e0 SEQUENCE:1 CREATED:20231206T091336Z DESCRIPTION: Nos últimos anos\, a comunidade científica tem vindo a acum ular provas conclusivas do aumento da polarização.Este crescimento não só implica que diferentes grupos não consigam chegar a um consenso sobre questões fundamentais\, como também se materializa em redes sociais mai s modulares - estruturas formadas por comunidades fracamente ligadas - que exacerbam os riscos de polarização\, mesmo em tópicos menos divisivos. Para abordar esta questão\, trabalhos anteriores priorizaram a identific ação dos mecanismos subjacentes responsáveis pela polarização social\ , tanto na composição das opiniões como no que respeita à organizaçã o estrutural das comunidades.No entanto\, que impacto tem a co-evolução de um processo de difusão de informação e da estrutura da rede em popul ações que já se encontram estruturalmente polarizadas? Será que amplif ica ou atenua o grau de polarização estrutural numa comunidade? Neste tr abalho\, é utilizado um modelo co-evolutivo de difusão de informação p ara compreender o impacto que as preferências individuais de religação têm nas estruturas modulares e em que condições esta dinâmica de adapt ação da rede pode levar a estrutura social a atingir um consenso.Demonst ra-se que os indivíduos com preferências de religação homofílicas pro movem o consenso para uma informação simples\, ao passo que os indivídu os com preferências de religação heterofílicas são mais eficientes na criação de pontes entre populações no caso de uma informação comple xa.Estes resultados sugerem que\, em redes sociais polarizadas\, uma combi nação de indivíduos com diferentes preferências de religação parece ser essencial para atenuar a polarização social. LAST-MODIFIED:20231206T091336Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/eventos/information-diffusion-on-dyna mic-networks/ X-ALT-DESC;FMTTYPE=text/html: Nos últimos anos\
, a comunidade científica tem vindo a acumular provas conclusivas do aume
nto da polarização.Este crescimento não só implica que diferentes grup
os não consigam chegar a um consenso sobre questões fundamentais\, como
também se materializa em redes sociais mais modulares - estruturas formad
as por comunidades fracamente ligadas - que exacerbam os riscos de polariz
ação\, mesmo em tópicos menos divisivos. Para abordar esta questão\, t
rabalhos anteriores priorizaram a identificação dos mecanismos subjacent
es responsáveis pela polarização social\, tanto na composição das opi
niões como no que respeita à organização estrutural das comunidades.
No entanto\, que impacto tem a co-evolução de um processo de dif
usão de informação e da estrutura da rede em populações que já se en
contram estruturalmente polarizadas? Será que amplifica ou atenua o grau
de polarização estrutural numa comunidade? Neste trabalho\, é utilizado
um modelo co-evolutivo de difusão de informação para compreender o imp
acto que as preferências individuais de religação têm nas estruturas m
odulares e em que condições esta dinâmica de adaptação da rede pode l
evar a estrutura social a atingir um consenso.
Demonstra-se que o
s indivíduos com preferências de religação homofílicas promovem o con
senso para uma informação simples\, ao passo que os indivíduos com pref
erências de religação heterofílicas são mais eficientes na criação
de pontes entre populações no caso de uma informação complexa.Estes re
sultados sugerem que\, em redes sociais polarizadas\, uma combinação de
indivíduos com diferentes preferências de religação parece ser essenci
al para atenuar a polarização social.
Perturbações de c
ampos em espaços-tempo com buracos negros são consideradas em vários co
ntextos\, desde a investigação da dinâmica de buracos negros astrofísi
cos até ao estudo de teorias de gravidade quântica. Um espaço-tempo per
turbado vibra com frequências características\, conhecidas como modos qu
asi-normais. Em espaços-tempo assimptoticamente anti-de Sitter (AdS)\, es
tes são estudados no contexto da correspondência AdS/teoria de campo con
formal (CFT)\, onde as frequências dos modos quasi-normais determinam a e
scala de tempo da termalização da CFT.
Nós estudamos perturbações de campos de Proca em espaços-tempo A
dS e Schwarzschild-AdS com d-dimensões. Obtemos as equações de Proca de
compondo o campo segundo o seu comportamento tensorial na esfera. Demonstr
amos que as equações formam dois setores completamente separados: o seto
r tipo-vetorial\, que engloba d-3 graus de liberdade desacoplados do campo
\, governados por uma única equação do tipo-onda\; o setor tipo-escalar
\, que descreve os restantes dois graus de liberdade do campo\, governados
por duas equações do tipo-onda acopladas.
Nós mostramos que
as últimas desacoplam em AdS com d dimensões\, e calculamos as soluçõe
s exatas de modos normais para perturbações de Proca neste espaço-tempo
\, impondo condições de fronteira de Dirichlet no infinito. Adicionalmen
te\, recuperamos os resultados para perturbações de Maxwell quando a mas
sa do campo de Proca tende para zero. A estabilidade linear em Schwarzschi
ld-AdS perante perturbações de Proca tipo-vetorial e monopolo é provada
. Também calculamos numericamente os modos quasi-normais de perturbaçõe
s de Proca em Schwarzschild-AdS com 4\,5\,6\,7 dimensões\, e desenvolvemo
s um estudo analítico do espetro para buracos negros pequenos.
The last years hav
e seen a rapid development of applications of quantum computationto quantu
m field theory. The first quantum algorithms for simulation of scattering
havebeen proposed in the context of scalar and fermionic theories\, requir
ing thousands oflogical qubits.
These algorithms are not suitabl
e to simulate scattering of incomingbound states\, as the initial state pr
eparation relies typically on adiabaticallytransforming wavepackets of the
free theory into wavepackets of the interactingtheory. In this talk\, I w
ill present a strategy to excite wavepackets of the interacting theorydire
ctly from the vacuum of the interacting theory\, allowing for preparation
of statesof composite particles that can be taken as initial states of a s
cattering simulation.
Thisis the first step towards digital quan
tum simulation of scattering of bound states.The approach is based on the
Haag-Ruelle scattering theory\, which provides a way toconstruct creation
and annihilation operators of a quantum field theory in a full\, nonpertur
bative framework. As an example\, I will consider a scalar theory in one s
pacedimension displaying a composite particle in its spectrum
ABSTRACT:
In the vicinity of black holes\, particle density can significantly increase\, acting as efficient transducers. This is evident in the superradiant generation of ultralight bosons\, which can attain Pl anck-scale field values.
Within this dense boson environment\, we witness the occurrence of non-perturbative particle production—a phenomenon previously associa ted primarily with the early-universe cosmology. This talk will explore th eir impact on various observational channels associated with black holes\, such as the high-energy neutrino observatories and Event Horizon Telescop e.
END:VEVENT BEGIN:VEVENT SUMMARY:MUSE-Faint: Dissecting the faintest galaxies with MUSE DTSTART:20231214T143000Z DTEND:20231214T160000Z DTSTAMP:20240329T082743Z UID:36f076b6-d110-4236-b44a-85ff328007de SEQUENCE:1 CREATED:20231211T160614Z DESCRIPTION:ABSTRACT: Ultra-faint dwarfs are the lowest mass and most dark -matter dominated systems known. The shallow potential wells make them sus ceptible to feedback from star formation and their low baryonic content al lows us to use their stars as test-particles in the dark matter potential. Here I will give an overview of the MUSE-Faint survey\, a MUSE GTO survey of 10 ultra-faint dwarfs. After introducing the survey\, I will outline h ow the high density of stellar spectra obtainable with MUSE can be used to constrain the dark matter content and density profiles of the galaxies an d discuss how the data can be used to constrain dark matter models and the details of galaxy formation models in the very most star poor dark matter halos known. LAST-MODIFIED:20231211T160614Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/muse-faint-dissecting-the-fai ntest-galaxies-with-muse/ X-ALT-DESC;FMTTYPE=text/html:ABSTRACT:
Ultra-faint dwarfs are the lowest mass and most dark- matter dominated systems known. The shallow potential wells make them susc eptible to feedback from star formation and their low baryonic content all ows us to use their stars as test-particles in the dark matter potential.
Here I will gi ve an overview of the MUSE-Faint survey\, a MUSE GTO survey of 10 ultra-fa int dwarfs. After introducing the survey\, I will outline how the high den sity of stellar spectra obtainable with MUSE can be used to constrain the dark matter content and density profiles of the galaxies and discuss how t he data can be used to constrain dark matter models and the details of gal axy formation models in the very most star poor dark matter halos known.
END:VEVENT BEGIN:VEVENT SUMMARY:Let's talk about... Applications of Particle Physics research DTSTART:20231214T170000Z DTEND:20231214T190000Z DTSTAMP:20240329T082743Z UID:84608e9b-4705-4b60-9c77-a0fc49c9ddd4 SEQUENCE:1 CREATED:20231207T135607Z DESCRIPTION: LAST-MODIFIED:20231207T135607Z LOCATION: URL:http://df.vps.tecnico.ulisboa.pt/eventos/lets-talk-about-applications- of-particle-physics-research/ END:VEVENT BEGIN:VEVENT SUMMARY:Plasmas in the semiconductor industry: modern trends\, opportuniti es and diversity DTSTART:20231215T110000Z DTEND:20231215T120000Z DTSTAMP:20240329T082743Z UID:aa304a4b-76dd-4779-ac72-c8eb08722035 SEQUENCE:1 CREATED:20231130T141623Z DESCRIPTION:Abstract:The semiconductor industry is moving towards ever inc reasing densities and ever decreasing feature sizes. This was kicked off 4 0 years ago\, by two international initiatives: Sematech in the USA and JE SSI in the European Union. Those initiatives have lasted for around 10 yea rs. After that\, the technology was mature\, and industry hardly needed th e input of academia for solving their technical challenges in the plasma d omain. In recent years\, since the moment that feature sizes came below 10 nm\, a revival of the field has been taking place. For example: vertical etching angle specifications ask for side wall angles between 89.6 and 90 degrees\, anisotropy has been approaching and now exceeds 100\, etc. This has evoked a new need of industry for input from plasma physics\, sheath p hysics\, fluid dynamics and surface physics and chemistry in these size re gimes (Knudsen flow\, single atom reactions\, etc). Recently\, the USA lau nched the CHIPS act\, a package of 45 G$ for semiconductor processing tech nology. Europe has a similar CHIPS-package. In the presentation the needs of modern-day semiconductor processing will be highlighted\, and we will a lso try to show how we\, as people in academia\, can cater to that need wh ile at the meantime performing cutting edge fundamental science. One of th e needs of the industry\, but also of academia\, is diversity. We need a w ell-trained workforce with a diverse composition. TU/e has embarked on a c ourse of increasing the diversity in the academic population. With that st rategy\, for instance\, the fraction of female staff in tenured academia i ncreased from 2 % to 35 % in 6 years in the physics department. We will de scribe the vital steps that have contributed to this spectacular shift. LAST-MODIFIED:20231130T141623Z LOCATION:Room 02.1 (floor -2\, Centro de Congresso IST) URL:http://df.vps.tecnico.ulisboa.pt/eventos/plasmas-in-the-semiconductor- industry-modern-trends-opportunities-and-diversity/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
The s
emiconductor industry is moving towards ever increasing densities and ever
decreasing feature sizes. This was kicked off 40 years ago\, by two inter
national initiatives: Sematech in the USA and JESSI in the European Union.
Those initiatives have lasted for around 10 years. After that\, the techn
ology was mature\, and industry hardly needed the input of academia for so
lving their technical challenges in the plasma domain.
In recent
years\, since the moment that feature sizes came below 10 nm\, a revival
of the field has been taking place. For example: vertical etching angle sp
ecifications ask for side wall angles between 89.6 and 90 degrees\, anisot
ropy has been approaching and now exceeds 100\, etc. This has evoked a new
need of industry for input from plasma physics\, sheath physics\, fluid d
ynamics and surface physics and chemistry in these size regimes (Knudsen f
low\, single atom reactions\, etc). Recently\, the USA launched the CHIPS
act\, a package of 45 G$ for semiconductor processing technology.
Europe has a similar CHIPS-package. In the presentation the needs of mod
ern-day semiconductor processing will be highlighted\, and we will also tr
y to show how we\, as people in academia\, can cater to that need while at
the meantime performing cutting edge fundamental science. One of the need
s of the industry\, but also of academia\, is diversity. We need a well-tr
ained workforce with a diverse composition.
TU/e has embarked on
a course of increasing the diversity in the academic population. With tha
t strategy\, for instance\, the fraction of female staff in tenured academ
ia increased from 2 % to 35 % in 6 years in the physics department. We wil
l describe the vital steps that have contributed to this spectacular shift
.
As alterações cli
máticas são causadas\, sobretudo\, pela queima de combustíveis fósseis
para satisfazer as nossas necessidades energéticas. Os edifícios são o
maior consumidor de energia na UE\, sendo responsáveis por 40% da energi
a que esta consome e por 36% das emissões de gases de efeito estufa relac
ionadas com energia\, logo NZEBs são necessários.
Neste trabal
ho\, em Polysun\, fizemos uma análise técnico-económica a um sistema de
aquecimento e arrefecimento com bomba de calor em quatro edifícios não-
residenciais que variam em tamanho (pequeno e médio) e condição (não-r
enovado e renovado)\, considerando a inclusão de energias solar térmica
e fotovoltaica. Devido à dificuldade em combinar energia solar térmica c
om a bomba de calor\, foi necessário requisitar água quente ao sistema p
ara este satisfazer as necessidades energéticas dos edifícios. No entant
o\, o sistema não é viável economicamente.
Pelo contrário\,
o sistema solar fotovoltaico é viável mesmo considerando apenas as neces
sidades de climatização dos edifícios. Definir uma temperatura de aquec
imento diferente quando o edifício não é ocupado melhorou o desempenho
do sistema\, enquanto a mesma abordagem para o arrefecimento originou resu
ltados inconclusivos. Quando consideramos o consumo global de eletricidade
dos edifícios\, os resultados económicos do sistema melhoram\, reduzind
o os custos totais em 25 anos em 29.7% a 34.3% sem vender eletricidade.
Além disso\, o sistema fornece entre 47.0% e 99.8% da eletricidad
e necessária para climatização e entre 51.9% e 66.2% da eletricidade to
tal consumida. Finalmente\, os edifícios renovados pequeno e médio têm
custos totais 11.8% e 17.1% inferiores aos dos edifícios não-renovados p
equeno e médio.
Resumo
Uma compreensão profunda de sistemas de matéria conden
sada foi alcançada assumindo uma periodicidade perfeita\, através do teo
rema de Bloch. No entanto\, quando a invariância translacional é quebrad
a\, podem manifestar-se fenómenos surpreendentes que não têm análogo n
o caso periódico. As estruturas quaseperiódicas\, caracterizadas por mod
ulações determinísticas incomensuráveis com a rede\, são um exemplo p
articularmente rico de sistemas não translacionalmente invariantes.
<
br/> Estes sistemas manifestam física intrigante\, desde propriedades de
localização exóticas a fenómenos de banda estreita correlacionados em
estruturas moiré como a bicamada de grafeno rodada. É crucial que\, embo
ra seja bem conhecido que as estruturas moiré são quase-periódicas em g
eral\, só recentemente o papel da quase-periodicidade começou a ser expl
orado nestes sistemas. Nesta dissertação exploramos as fases quânticas
de estruturas quase-periódicas e moiré de uma forma unificada.
Começamos por explorar as propriedades de localização de modelos quase
-periódicos de rede genéricos. Primeiramente\, mostramos que transiçõe
s genéricas de deslocalização-localização em modelos unidimensionais
sem interação partilham um mecanismo comum baseado na emergência de dua
lidades ocultas entre as fases estendida e localizada. Adicionalmente\, de
senvolvemos uma descrição universal das propriedades de localização de
stes sistemas e usamo-la para capturar analiticamente diagramas de fase de
localização para uma ampla classe de modelos.
Por fim\, desen
volvemos uma generalização a muitos corpos desta teoria para abordar as
propriedades de localização no estado fundamental de Hamiltonianos unidi
mensionais quase-periódicos com interacções. Finalmente\, estudamos o p
apel da quase-periodicidade em estruturas de moiré. Analisando um modelo
de tight-binding da bicamada de grafeno rodada\, mostramos que a quase-per
iodicidade cria uma fase sub-balística no regime de banda estreita não i
nteractuante.
Adicionalmente\, estudamos um sistema de moiré un
idimensional com interacções\, que contém uma fase multifractal crític
a muito semelhante à fase sub-balística da bicamada de grafeno rodada. M
ostramos que\, apenas quando o sistema é quase-periódico\, esta fase é
instável à criação de uma nova fase ordenada após a adição de inter
acções. Esta dissertação oferece duas contribuições principais.
Por um lado\, fornece uma compreensão unificada de diferentes model
os de rede quase-periódicos e um novo conjunto de ferramentas para estuda
r os seus diagramas de fases. Por outro lado\, ao estabelecer a quase-peri
odicidade como um possível ingrediente importante nos sistemas moiré e o
seu potencial para criar novos estados da matéria\, marca o início da e
xploração de possibilidades excitantes ainda por descobrir no campo emer
gente dos sistemas de moiré quase-periódicos.
A microfluídica su
rgiu como uma ferramenta que permite a miniaturização de processos labor
atoriais e o desenvolvimento de dispositivos Lab-On-a-Chip (LOC). Estas pl
ataformas em microescala oferecem vantagens significativas\, incluindo vol
umes reduzidos de amostras e reagentes\, automatização de processos e re
sultados rápidos e reprodutíveis.
Os métodos tradicionais de marcação magnética tipicamente envolvem o
uso de vários instrumentos laboratoriais especializados\, resultando em t
empos prolongados (numa escala de horas/dias) desde a recolha de amostra a
té à sua análise - uma preocupação significativa em situações que e
nvolvem ameaças biológicas\, como o antraz\, a tuberculose e a legionelo
se. Este trabalho\, que faz parte de um projeto a decorrer no INESC MN\, e
nfrenta esse desafio introduzindo um circuito microfluídico para prepara
ção de amostras\, que é compacto (largura_38650×altura_50×comprimento
_50320 μm3) e consegue completar o processo de marcação magnética em m
enos de 5 minutos\, tornando-o adequado para aplicações de point-of-care
(POC).
Dentro deste circuito\, dua
s suspensões - a amostra biológica e nanopartículas magnéticas – sã
o introduzidas e interagem dentro de um misturador (l_12600×a_50×c_18240
μm3\, com obstáculos) para ligação das nanopartículas aos analitos b
iológicos\, ostentando uma eficiência de mistura simulada de >\;99%. O
uso subsequente de um separador magnético (l_5650×a_50×c_23740 μm3) c
urva a trajetória das espécies magnéticas\, tendo-se obtido um resultad
o de >\;80% de conteúdo de ferro que flui através do circuito em compa
ração com o descartado como resíduo. Esta separação seletiva elimina
com sucesso analitos não marcados. A amostra marcada magneticamente entra
depois num separador por dimensões (l_800×a_50×c_8450 μm3\, com obst
áculos)\, refinando ainda mais o processo e separando os analitos marcado
s de nanopartículas magnéticas livres\, que são significativamente meno
res. Depois da amostra marcada passar por este circuito\, esta segue para
o citómetro magnético para análise.
Pretende-se com esta abordagem integrada oferecer uma solução rápi da e eficiente para preparar e analisar amostras biológicas marcadas magn eticamente. Ao reduzir a complexidade do processo de preparação de amost ras e facilitar a integração com\, por exemplo\, um coletor de aerossói s e um citómetro magnético\, este sistema possui grande potencial em apl icações POC em saúde pública\, monitorização ambiental\, entre outro s.
END:VEVENT BEGIN:VEVENT SUMMARY:Quantum simulation of quasicrystals with ultracold quantum gases: The Bose side DTSTART:20231220T143000Z DTEND:20231220T160000Z DTSTAMP:20240329T082743Z UID:8594c163-5466-48d4-b314-9fc79c059522 SEQUENCE:1 CREATED:20231219T120005Z DESCRIPTION:Quasicrystals\, an exotic class of materials with long-range b ut nonperiodic order\,exhibit fascinating properties due to their unique p osition at the crossroads of longrange-ordered and disordered systems. The se include remarkable localization andfractal properties. Quantum simulati on of quasicrystals in synthetic bosonic matternow paves the way to the ex ploration of these intriguing systems in wide parameterranges. This talk w ill review recent progress in the field of quantum simulation ofquasicryst als with ultracold-atom gases. Particular attention will be paid to theeme rgence of the still-elusive Bose glass phase. Previously\, clear observati on of thisemblematic phase has been thwarted by thermal fluctuations\, whi ch compete withquasi-disorder. But recent work shows that the use of shall ow quasicrystal potentialspermits to overcome this pitfall\, and Bose glas s phases can be stabilized in broadtemperature regimes\, in 1D as well as 2D. Theoretical aspects and experimentalperspectives will be discussed. LAST-MODIFIED:20231219T120005Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/quantum-simulation-of-quasicr ystals-with-ultracold-quantum-gases-the-bose-side/ X-ALT-DESC;FMTTYPE=text/html:Quasicrystals\, an
exotic class of materials with long-range but nonperiodic order\,exhibit f
ascinating properties due to their unique position at the crossroads of lo
ngrange-ordered and disordered systems. These include remarkable localizat
ion andfractal properties. Quantum simulation of quasicrystals in syntheti
c bosonic matternow paves the way to the exploration of these intriguing s
ystems in wide parameterranges.
This talk will review recent pro
gress in the field of quantum simulation ofquasicrystals with ultracold-at
om gases. Particular attention will be paid to theemergence of the still-e
lusive Bose glass phase. Previously\, clear observation of thisemblematic
phase has been thwarted by thermal fluctuations\, which compete withquasi-
disorder.
But recent work shows that the use of shallow quasicry
stal potentialspermits to overcome this pitfall\, and Bose glass phases ca
n be stabilized in broadtemperature regimes\, in 1D as well as 2D. Theoret
ical aspects and experimentalperspectives will be discussed.
Quantum Annealing h
as proven to be a powerful tool to tackle several optimizationproblems. Ho
wever\, its performance is severely impacted by the limited connectivityof
the underlying quantum hardware\, compromising the quantum speedup. In th
iswork\, we present a novel approach to address these issues\, by describi
ng a method toimplement non-local couplings throught the lens of Local Ope
rations and ClassicalCommuncations (LOCC).
Non-local couplings a
re very versatile\, harnessing theconfigurability of distributed quantum n
etworks\, which in turn lead to greatenhancement of the physical connectiv
ity of the underlying hardware. Furthermore\,the realization of non-local
couplings between distrinct quantum annealing processorsactivates the scal
ability potential of distributed systems\, i.e. allowing for a distributed
quantum annealing system.
Finally\, in a more distant vision\, w
e also show that securemulti-party quantum annealing algorithms are possib
le\, allowing for cooperation ofdistrusting parties through optimization w
ith quantum annealing and a particular typeof non-local couplings.
During this talk\,
we will explore how conserving quantities influence the long-timedynamics
of generally strongly interacting closed systems. Typically\, interactingq
uantum systems achieve thermalization via their own unitary dynamics\, lea
ding tothe emergence of statistical mechanics. However\, the route to equi
librium can differdue to the existence of conserved quantities.
Often\, conserved charges spread diffusively across the system. However\,
mobilityconstraints can impede or even halt their dynamics. The initial pa
rt of the talk isdevoted to the non-equilibrium dynamics of fractonic syst
ems\, especially those withmultiple conservation laws\, such as dipole con
servation. In these systems\, charges areunable to move independently.
Their limited dynamics are described by a generalizeddiffusion equa
tion that exhibits sub-diffusion [1]. In the second half of the talk\, ins
pired by recent experiments on trapped-ion platformsthat intrinsically dis
play power-law decaying interactions [2]\, we will delve into theinterplay
between long-range interactions that promote thermalization and the dipol
emobility constraints that obstruct it [3].
Em alguns dos mais
importantes problemas por resolver na física de partículas\, a resposta
mais provável surge da adição de novas partículas ao Modelo Padrão. N
ovos bosões de Higgs são frequentemente o ponto de partida para novos mo
delos. Estes\, por sua vez\, precisam de ser limitados teoricamente atrav
és da unitariedade nas teorias quânticas de campo\, quer por limites de
parâmetros\, quer por regras de soma de amplitudes.
Introduzimo
s um novo método computacional para estabelecer limites de unitariedade e
m modelos escalares e calculamos esses limites em modelos de três dubleto
s de Higgs. Recorremos a regras de soma de unitariedade em modelos de fot
ões escuros descobrindo que a unitariedade define um novo parâmetro de p
recisão. Com ele\, restringimos os modelos de mat´eria escura\, apontand
o para uma dependência específica entre a física do bosão Z e a estrut
ura do novo sector escalar.
Em muitos casos\, os modelos de mat
éria escura podem ser excluídos. Estudamos a teoria invariante no contex
to de modelos de multiplos dubletos de Higgs\, calculando a série de Hilb
ert do modelo de trˆes dubletos de Higgs pela primeira vez usando o cálc
ulo Omega. Encontramos vários resultados da teoria dos invariantes aplic
áveis a modelos de múltiplos dubletos de Higgs\, tais como a contagem de
parâmetros nos casos geral e simétrico.
Finalmente\, usamos a
teoria dos invariantes para estudar o puzzle de sabor do Modelo Padrão.
O enigma do sabor é reformulado num quadro completamente invariante e sim
plificamos resultados anteriores sobre as relações entre os invariantes
que violam CP\, e os que não violam CP. O trabalho sobre estas duas class
es de tópicos (limites de unitariedade e teoria dos invariantes) resultou
numa série de publicações que vão desde propriedades matemáticas abs
tratas que restringem as teorias físicas ate `a comparação pormenorizad
a com a experiencia.
ABSTRACT: The prosp
ect of a stochastic gravitational wave (GW) background from the primordial
universe offers a promising new window for cosmology and fundamental phys
ics. Studying the GW signals from cosmological phase transitions can illum
inate aspects of Beyond the Standard Model (BSM) physics and allow us to p
robe the early universe via a new perspective.
In this study (23
09.08530)\, we investigated minimal scalar BSM extensions\, with respect t
o the evolution of the scalar potential at the end of inflation. More spec
ifically\, we focussed on the transition from the typical potential-domina
ted de Sitter epoch to the kinetic dominated period dubbed kination.
<
br/> In this setting\, a strong first-order phase transition can take plac
e because of the scalar field'\;s decreasing potential barrier due to
its non-minimally coupling to gravity. Therefore\, a characteristic GW spe
ctrum can be produced from the collision of true-vacuum bubbles. With this
prescription\, we propose a new triggering mechanism for BSM phase transi
tions that could produce potentially observable GW signatures with the fut
ure detectors.
Abstract: Textile t
riboelectric nano-generators (TENGs) are promising solution for wearable\,
self-powered sensing technology. However\, to develop textile TENGs with
high output power in adaptable devices using industrial textile compatible
techniques for embedded textile electronics is still challenging.
In this work\, a flexible triboelectric textile is developed by using p
rinted graphene electrodes and the textile as a triboelectric pair with di
fferent deposition methods. The flexible TENG exhibits steady output perfo
rmance under heavy deformation and their sensitivity to movement was inves
tigated as a wearable sensor to monitor biomechanical movements.
This work paves the door for the seamless incorporation of self-powered w
earable sensing technology into textiles by offering a flexible method for
creating flexible triboelectric textile fabrics using industrially suitab
le printing textile processes.
A aceleração bas
eada em plasma (ABP) poderá reduzir significativamente a dimensão e/ou o
custo dos colisores de partículas\, que têm sido instrumentais para obt
er descobertas fundamentais na física e cujos limites técnicos se está
a tornar cada vez mais dispendioso desafiar. Os conceitos de ABP dependem
frequentemente da capacidade de manipular interações complexas entre fei
xe e plasma. Num desses conceitos\, direcionado a aplicações na física
de alta energia e que está a ser testado na experiência AWAKE no CERN\,
a onda de plasma usada para aceleração é impelida por um feixe de part
ículas longo e altamente energético.
Neste caso as interaçõe
s em causa são as instabilidades de hosing e de automodulação. A instab
ilidade de auto-modulação (IAM) pode ser utilizada para produzir campos
de esteira (wakefields) de alta amplitude a partir de um feixe longo\, que
de outra forma não seria adequado para excitar a onda de plasma. A insta
bilidade de hosing (IH) é indesejada\, porque pode deteriorar o feixe e a
estrutura do campo de esteira. Nesta dissertação\, começamos por rever
e alargar a teoria que descreve estas instabilidades. Utilizamos simulaç
ões particle-in-cell com o código OSIRIS para testar a robustez da IAM\,
especialmente após a sua saturação\, a flutuações das condições in
iciais.
A dependência das taxas de crescimento da IH e da IAM d
a frequência de perturbação é determinada para um regime adiabático e
um regime inicial. Durante este regime inicial\, mostramos que ambas as i
nstabilidades podem ser interpretadas como osciladores harmónicos forçad
os\, e que é possível controlar o seu crescimento ao "\;desafinar&qu
ot\; a oscilação do plasma em resposta a uma perturbação do envelope (
IAM) ou do centroide (IH) do feixe suficientemente cedo. No caso da IAM re
velamos ainda um fenómeno de ressonância sub-harmónica. Todos estes res
ultados são validados com simulações. Esta nova compreensão do crescim
ento de instabilidades feixe-plasma pode ter implicações importantes par
a os aceleradores baseados em plasma.
The notion of convo
lution of two probability vectors can be extended to operationsdetermined
by multistochastic tensors\, to describe Markov chains of a higher order.
Onthe other hand\, the idea of convolution lies in the centre of machine l
earningalgorithms for image processing: Convolutional Neural Networks.
In my talk\, I will firstpresent the characterization of the probab
ility eigenvectors of multi-stochastictensors\, corresponding to fixed poi
nts of generalized Markov chains. Similar results willbe also obtained in
the quantum case for multi-stochastic channels acting on mixedquantum stat
es.
Next\, I propose a quantum analogue of the convolution\, bas
ed oncoherifications of tristochastic tensors\, defined for two arbitrary
density matrices ofthe same size. Finally\, I will discuss possible applic
ations of this notion to constructschemes of error mitigation or as buildi
ng blocks in quantum Convolutional NeuralNetworks..
Abstract:
A th
in circular structure\, a string loop\, vibrating in the central plane of
a Schwarzschild black hole will be investigated. String loop stability and
frequencies of its vibrational modes will be provided for different strin
g equations of state.
String are objects with tension and hence
they can help us to understand the problem of relativistic elasticity\; th
ey can be also considered as simplified models for thin magnetic flux tube
s from plasma physics. We used the vibrating string loop model to fit the
quasi-periodic oscillation observed in X-ray signals coming from some comp
act sources.
As fontes de raios
X mais avançadas\, tais como os lasers de electrões livres e os sincrot
rões\, permitem sondar e obter imagens de processos ultra-rápidos que oc
orrem às mais ínfimas escalas atómicas e moleculares. Estas fontes são
dispositivos de grandes dimensões\, normalmente da ordem de alguns quil
ómetros. Recentemente\, têm sido feitos esforços para desenvolver solu
ções mais pequenas e económicas\, maioritaraimente baseadas em feixe-pl
asma. Nesta tese\, exploramos as fontes de radiação baseadas em plasma u
sando teoria e simulações Particle-In-Cell\, baseando-nos nas possibilid
ades abertas pela recente descoberta da Superradiância Generalizada para
propor novos métodos de geração de impulsos de radiação intensos\, ul
tra-curtos e de alta frequência.
Nomeadamente\, investigámos a
radiação proveniente de partículas que atravessam campos evanescentes.
Estes modos de superfície são comuns em experiências de interação la
ser-plasma. Tirámos partido da localização espacial extrema das ondas e
vanescentes para gerar raios-X dirigidos e demonstrámos que os electrões
com g '\; 10100 que atravessam uma onda evanescente podem produzir ra
diação KeV-MeV. Além disso\, mostrámos que a posição de intersecçã
o entre o feixe de electrões e a onda evanescente pode atuar como uma par
tícula virtual. Nas condições certas\, esta partícula virtual pode ser
superluminosa e produzir um choque ótico superradiante.
Além
disso\, explorámos a radiação coerente de betatrões através de superr
adiância generalizada. Onde uma manipulação espácio-temporal do feixe
de partículas aceleradas pode levar à emissão superradiante. Mostrámos
que um feixe de partículas com uma modulação sinusoidal com uma veloci
dade de fase superluminal pode produzir choques ópticos ao longo do ângu
lo de Cherenkov associado à velocidade de fase da modulação. Estes choq
ues ópticos conduzem a impulsos ultra-curtos de nível de attossegundo cu
ja intensidade cresce quadraticamente com o número de partículas no feix
e\, independentemente da distância entre as partículas.
Durant
e a realização desta tese\, baseámo-nos fortemente no RaDiO e introduzi
mos várias melhorias neste código. Uma das mais importantes foi acompati
bilidade com GPU utilizando a linguagem de programação CUDA. Utilizando
uma única placa de GPU\, conseguimos cálculos de radiação quase instan
tâneos em milhões de células espaciais\, um feito que anteriormente só
era possível quando se utilizavam clusters de computadores com centenas
de CPUs. Esta melhoria permitiu-nos executar inúmeras simulações de rad
iação\, anteriormente dispendiosas\, permitindo observar a radiação a
resoluções espaciais sem precedentes.
Abstract: he Pierr
e Auger Observatory\, the world'\;s largest experiment in the study of
the highest energy astroparticles\, is currently undergoing an upgrade to
enhance its UHE cosmic ray detection capabilities further. On the other h
and\, the Southern Wide-field Gamma-ray Observatory\, a next-generation ex
periment aiming to look for PeVatron sources in the centre of our Galaxy\,
is currently on an R&\;D phase to concept\, design and plan its constr
uction at a high altitude in South America.
Given the energy o
verlap between these observatories and their current set of conditions\, t
here is a privileged opportunity to explore strategies to boost the capabi
lities of the Pierre Auger Observatory and the SWGO in detecting astropart
icle multi-messenger phenomena. In this presentation\, I will discuss the
efforts aimed at enhancing the multi-messenger capabilities of both gamma-
ray array observatories.
Specifically\, I will demonstrate how t
hese observatories can efficiently detect astrophysical neutrinos without
incurring additional costs\, by leveraging inclined shower events. Additio
nally\, I will illustrate how the energy thresholds of these observatories
can be lowered through the implementation of a dedicated trigger strategy
. Furthermore\, novel gamma/hadron discrimination observables will be intr
oduced\, showcasing their ability to surpass muon counting in arrays simil
ar to SWGO\, while also exhibiting promising performance in larger\, spars
er arrays like the Pierre Auger Observatory.
The past years have
seen a growing interest in plasma-based accelerator technology since it p
rovides a route to more compact\, ecological yet powerful accelerators. Ho
wever\, even well-established acceleration techniques [1\, 2] are only eff
ective with particles traveling at speeds close to the speed of light (rel
ativistic particles)\, leading to the exclusion of heavier particles (with
respect to electrons)\, e.g. muons [3] or pions from the acceleration p
rocess.
In this PhD work\, we propose an innovative method to fi
ll this gap. We exploit structured light pulses with variable group veloci
ties [4\, 5\, 6]\, to demonstrate\, with theory and numerical calculations
\, that such property\, combined with a tailored density profile [7] for t
he plasma\, can give us the necessary control over the velocity of the wak
e to unlock the possibility of accelerating these particles from non-relat
ivistic to relativistic velocities in a single acceleration stage in a pla
sma accelerator.
Furthermore\, our ongoing research explores the
potential application of plasma-based acceleration technology in coherent
radiation production. We investigate the development of instabilities as a
long particle beam propagates through a plasma\, that is a possible way o
f generating coherent radiation.
ABSTRACT: By solvi
ng the Einstein'\;s field equations\, we derive several configurations
of compact objects with a nuclei of exotic energy in a static and spheric
ally symmetric spacetime. In this talk I describe the derivation and sever
al properties of the configurations\, including the fact that in some of t
hese objects can be reached a compacity as close to the black hole as desi
red\, and the configurations remain without singularities or horizons.
I present the evolution of some of the configuration which describe
interesting dynamical spacetimes which seems to maintain the configuratio
n at least for the time of the numerical evolution. I conclude mentioning
some ideas which can be tested in these peculiar configurations.
Abstract:
The
Scattering and Neutrino Detector at the LHC (SND@LHC) is the most recent experiment install
ed at CERN'\;s LHC. It intends to further branch out the capabilities
of the LHC by\, for the first time ever\, studying collider neutrinos\, pr
oduced with previously unseen energies.
Following a rapid constr
uction\, installation\, and commissioning phase\, we were able to successf
ully take data at the start of Run3\, in 2022 and 2023. Two dedicated te
st-beam campaigns for detector calibration were also carried out. Followin
g the first observation of muon collider neutrinos last year\, alongside F
ASERν\, the collaboration is making strides towards the first measurement
s of neutrinos produced at the LHC. Bridging the gap between the test-beam
calibrations and the data acquired from the LHC collisions will allow the
first energy dependent measurements.
Os processos de ext
ração de energia de buracos negros têm sido estudados para diferentes e
spaços-tempo. A extração de energia é possível através do decaimento
de partículas no interior da ergo-região\, processo de Penrose\, ou a p
artir de colisões entre partículas na vizinhança do horizonte de evento
s\, efeito BSW.
Estes mecanismos têm sido considerados para bur
acos negros carregados ou em rotação. Como algumas teorias atuais envolv
em números mais elevados de dimensões espaciais\, como a teoria de corda
s\, ou requerem uma constante cosmológica\, por exemplo no contexto da co
njetura AdS-CFT\, é de extrema importância o estudo destes processos de
extração de energia num formalismo genérico. Estes dois processos são
aqui estudados para três espaços-tempo diferentes. Primeiro\, considera-
se um espaço tempo de Reissner‑Nordström\, assintoticamente plano\, co
m d dimensões.
O processo de Penrose é analisado para e
ste espaço-tempo e\, em particular\, as condições necessárias para a o
corrência de uma bomba de buraco negro são estabelecidas. O efeito BSW
é considerado posteriormente\, para o mesmo espaço-tempo\, para o qual d
iferentes cenários de extração de energia são estudados. De seguida\,
consideramos os mesmos processos num espaço-tempo de Reissner-Nordström-
AdS.
Especificamente\, focamo-nos no efeito de uma constante cos
mológica negativa no estabelecimento de uma cadeia recursiva de decaiment
os no interior da ergo-região\, sem requerer um espelho refletor. O efeit
o BSW é também analisado para este espaço-tempo e comparado com o limit
e de constante cosmológica nula. Por último\, o mecanismo BSW é estudad
o na presença de uma constante cosmológica positiva e os resultados são
comparados com os dois cenários anteriores.
We present our stu
dies of the scrape-off layer (SOL) at ASDEX Upgrade\, focusing on the beha
vior of the inboard SOL in different magnetic configurations and the dynam
ics of the high-density region near the inboard plasma edge. Understanding
SOL behavior is essential to manage heat exhaust and achieve a detached o
peration in current and future reactors.
We investigate the exis
tence of hollow density profiles at the inboard midplane SOL by combining
several diagnostics and using a novel interpretation of reflectometry data
that relies on analyzing the spectral signatures of the beat signal. We s
how that the poloidal density asymmetry can influence line-integrated meas
urements\, such as interferometry\, and should be included in an integrate
d data analysis.
We investigate the role of the magnetic configu
ration in shaping the inboard SOL profile\, particularly as the plasma app
roaches a double-null configuration typical of many reactor designs. Our i
nvestigations reveal a narrowing of the inboard SOL profile\, driven by th
e magnetic disconnection from the outboard SOL\, underscoring the importan
ce of magnetic topology and parallel heat conduction in determining the in
board SOL properties.
We see a steep density gradient at the sec
ondary separatrix in both the midplane and divertor regions\, which we att
ribute to the presence of the inboard high-density region\, observable usi
ng reflectometry and Thomson scattering diagnostics. Near double-null\, a
drastic reduction in conducted heat to the inboard SOL leads to decreased
electron and neutral density in the inboard divertor.
Lastly\, w
e observe that the high-density region is significantly suppressed in unfa
vorable field configurations. We use these scenarios to measure the edge d
ensity decay length at the inboard and outboard midplane. We estimate a co
nsistently larger outboard decay length than the inboard side\, with an av
erage ratio of 1.7\, corroborating the expected ballooning nature of radia
l transport in tokamaks.
Alguns isótopos d
e gases nobres têm spins nucleares com tempos de coerência extraordiname
nte longos\, que excedem horas a temperatura ambiente. Embora sejam optica
mente inacessíveis\, podem interagir indiretamente com a luz\, usando át
omos de metais alcalinos como intermediários.
Investigamos a po
ssibilidade de realizar uma memória quântica óptica em misturas de gase
s nobres e alcalinos\, estudando os efeitos da difusão através de simula
ções numéricas\, e propomos um protocolo multi-modo inspirado no Atomic
Frequency Comb (AFC)\, com aplicações entusiasmantes em comunicação q
uântica a longas distâncias.
Adicionalmente\, mostramos que es
tes sistemas são uma plataforma promissora para estudar correlações qu
ânticas em sistemas de muitos corpos\, propondo uma experiência para det
etar a presença e profundidade de entrelaçamento e correlações de Bell
por meio de medições coletivas apenas. Em contraste com as experiência
s realizadas até à data\, a nossa proposta não requer temperaturas crio
génicas e prevê a observação de correlações de Bell numa escala verd
adeiramente macroscópica\, aumentando a sua duração e número de partí
culas em mais de dez ordens de grandeza.
ABSTRACT: Hawking s
howed that a black hole formed by collapse will emit radiation and eventua
lly disappear. We address the challenge to define an objective notion of p
hysical entropy which increases throughout this process in a way consisten
t with unitarity.
We have suggested that (instead of coarse-grai
ned entropy) physical entropy is matter-gravity entanglement entropy and t
hat this may offer an explanation of entropy increase both for the black h
ole collapse and evaporation system and also for other closed unitarily ev
olving systems. For this to work\, the matter-gravity entanglement entropy
of the late-time state of black hole evaporation would have to be larger
than the entropy of the freshly formed black hole. We argue that this may
possibly be the case due to (usually neglected) photon-graviton interactio
ns.
ABSTRACT: In this talk I will discuss how a free field in a cavity with moving boundaries ca n be used to theoretically and experimentally study Hawking radiation. Con cretely\, I will show that i) a finite period of acceleration of one of th e mirrors mimics a black to white hole dynamical geometry\, ii) the end st ate of the field shows thermal properties determined by the acceleration o f the trajectory of the mirror\, iii) this setting can\, in principle\, be implemented experimentally with current technology.
END:VEVENT BEGIN:VEVENT SUMMARY:Efficiency boost of electrochemical energy conversion by bifunctio nal catalysis DTSTART:20240313T143000Z DTEND:20240313T160000Z DTSTAMP:20240329T082743Z UID:cf8a5797-4428-4e13-86cb-3d3d65669b31 SEQUENCE:2 CREATED:20240312T155105Z DESCRIPTION:Abstract:The increased demand for energy in recent decades and the depletion of fossil fuel reserves have led to the need for new and cl ean power sources that will be used in the future. There are various propo sed alternatives to technologies based on fossil fuels\, but one of the mo st popular is use of electrochemical energy conversion and storage devices . However\, the design of efficient electrocatalysts for these devices rep resents a great challenge for the scientific community. Our research is fo cused on the development of bifunctional catalysts based on transition met al oxides (Mn\, Ni\, and Ti) for oxygen reduction and evolution of oxygen in an alkaline environment. These two reactions are the limiting factor in the functioning of electrochemical devices due to their slow kinetics on most electrode materials. Designing bifunctional electrocatalysts necessar y for the operation of metal-air batteries and regenerative fuel cell devi ces that combine a fuel cell and an electrolytic cell represents a special challenge - the same material should possess high activity and stability under both cathodic and anodic polarization conditions. The results obtain ed so far show an excellent performance of catalysts on transition metal o xides decorated with platinum\, where activity similar to that of commerci al Pt/C was achieved with half the amount of platinum in the synthesized e lectrocatalysts. Besides high activity\, these materials also showed great er stability than conventional carbon-supported electrocatalysts. LAST-MODIFIED:20240312T155144Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/efficiency-boost-of-electroch emical-energy-conversion-by-bifunctional-catalysis/ X-ALT-DESC;FMTTYPE=text/html:Abstract:
The i
ncreased demand for energy in recent decades and the depletion of fossil f
uel reserves have led to the need for new and clean power sources that wil
l be used in the future. There are various proposed alternatives to techno
logies based on fossil fuels\, but one of the most popular is use of elect
rochemical energy conversion and storage devices.
However\, the
design of efficient electrocatalysts for these devices represents a great
challenge for the scientific community. Our research is focused on the dev
elopment of bifunctional catalysts based on transition metal oxides (Mn\,
Ni\, and Ti) for oxygen reduction and evolution of oxygen in an alkaline e
nvironment.
These two reactions are the limiting factor in the f
unctioning of electrochemical devices due to their slow kinetics on most e
lectrode materials. Designing bifunctional electrocatalysts necessary for
the operation of metal-air batteries and regenerative fuel cell devices th
at combine a fuel cell and an electrolytic cell represents a special chall
enge - the same material should possess high activity and stability under
both cathodic and anodic polarization conditions.
The results ob
tained so far show an excellent performance of catalysts on transition met
al oxides decorated with platinum\, where activity similar to that of comm
ercial Pt/C was achieved with half the amount of platinum in the synthesiz
ed electrocatalysts. Besides high activity\, these materials also showed g
reater stability than conventional carbon-supported electrocatalysts.
Abstract:
Some of the most important and fascinating phenomena
in plasmas are related to kinetic effects\, like e.g. collisionless heatin
g or transport phenomena. Naturally\, the distribution functions of the ch
arged particles are at the heart of the problem. The distribution function
is a result of the complex interaction of the particles with the gas atom
s/molecules and the electric field structure.
On the other hand
\, the electric field structure itself is usually resulting from the coupl
ing to the electrons. Further\, in low-temperature plasmas\, the non-equil
ibrium conditions in these systems lead in general to distribution functio
ns which deviate significantly from the standard Maxwellian distribution.
While the common way of addressing kinetic effects is based on
the use of the Boltzmann equation\, an alternative approach for describin
g local Ohmic and non-local (stochastic) heating is provided by the Fokker
-Planck equation supplemented by the Langevin equation. One advantage of t
his approach\, as compared to the Boltzmann equation\, is probably a more
natural insight into the physics.
Local and non-local interacti
ons of electrons with fields are illustrated by selected examples. This in
cludes the problem of self-consistent field structures\, global distributi
on functions as well as tailored periodic field structures. Last not least
\, it will be shown that non-local effects can be important even under con
ditions of high collisionality. Finally\, an outlook for further work on k
inetic effects will be provided.
ABSTRACT: It is we
ll known that spinning black holes (BHs) are unstable under ultralight mas
sive bosonic perturbations. Due to this so-called superradiant instability
\, a macroscopic bosonic condensate can form around the BH\, leading to st
riking observable signatures\, such as the emission of detectable gravitat
ional waves from the condensate itself.
Hence\, this phenomenon
represents a powerful tool to probe ultralight fields beyond the Standard
Model\, such as axions or dark photons. Until recently\, studies of the in
stability assumed the superradiant field to be free from interactions\, as
ide from a minimal coupling to gravity. However\, as number densities can
reach extreme values in the process\, the effect of interactions can be cr
ucial\, even for very feebly interacting fields.
In particular\,
interactions with the ambient plasma environment (namely an accretion dis
k or interstellar plasma) or couplings to other Standard Model fields can
dramatically change the evolution of these systems. In this talk\, I will
describe the role of interactions and environmental effects in different s
uperradiant systems\, showing their impact in the evolution of the instabi
lities.
ABSTRACT:
Open Clusters are gravitationally bound associations
of stars that have been born together\, thus sharing the same age and che
mical composition. For these reasons\, they represent the ideal laboratori
es to perform studies in a broad range of fields such as Galaxy structure
and its evolution\, stellar evolution\, and gravity. The advent of the Gai
a mission\, culminating in Gaia DR3 with over 1.8 billion sources\, has si
gnificantly expanded our ability to detect and characterize open clusters\
, resulting in more than 10\,000 new candidates by 2023.
As astr
onomy transitions into the Big Data era\, the integration of Machine Learn
ing algorithms becomes crucial for the automated detection and analysis of
these clusters. In this seminar\, I will explore existing tools\, highlig
hting their advantages\, limitations\, potential pitfalls\, and their impl
ications on research outcomes.
I will also discuss some methods
useful to perform sanity checks on these algorithms (e.g. using t-Distribu
ted Stochastic Neighbour Embedding\; t-SNE maps). Furthermore\, I will pre
sent an innovative approach using an Artificial Neural Network (Machine Le
arning algorithms inspired by biological neural networks) in conjunction w
ith Quad-Trees (tree data structure mapping 2D data to 1D) to determine th
e age\, extinction\, and distance of open clusters.
Abstract:
The last 25 years have seen wonderful times in high a
ngular resolution\, optical/infrared ground-based astronomy: active optics
enabled ever larger telescopes\, adaptive optics now routinely remove the
image blur from the turbulent earth atmosphere\, and integral field spect
roscopy adds the third\, spectral dimension to highest resolution imaging.
And most recently\, optical/infrared interferometry brought yet
another revolution by synthesizing a telescope with an equivalent diamete
r of a hundred meter and more. We will describe the development and advanc
es in the field\, and especially the pioneering GRAVITY instrument.
Our presentation tak
es us from exoplanets all the way to distant quasars\, with special focus
on the Galactic Center and tests of the massive black hole paradigm. The o
ngoing upgrades will soon boost optical interferometry to the next level\,
opening up the extragalactic sky for milli-arcsecond resolution interfero
metric imaging. We will end with an outlook on expanding optical interfero
metry to kilometer wide arrays\, which will be hundred to thousand times s
harper than even the largest single dish telescopes.
ABSTRACT:
The extinction and interstellar polarization (ISP) i
n reddened supernovae (SNe) tend to show different properties from those a
veragely observed in the Milky Way (MW)\, displaying smaller total-to-sele
ctive extinction ratios and polarization maxima at shorter wavelengths. Th
is can be interpreted as their host galaxies contain dust grains whose pro
perties are substantially different from the MW dust (IS dust scenario).
Another possible explanation is that this peculiarity is created
by the effects of the multiple scatterings of the SN light by circumstella
r (CS) dust grains (CS dust scenario). Clarifying the origin of the non-MW
-like extinction and ISP is important not only for performing the precise
reddening correction but also for understanding the dust properties in the
host galaxies of SNe.
In this talk\, I will quantitatively demo
nstrate what kinds of peculiar extinction and ISP can be realized by these
scenarios with close attention to the difference between different types
of SNe\, and identify the origin by comparing these theoretical prediction
s with observed extinction and ISP in reddened SNe. Based on the conclusio
n on this origin\, I will discuss the dust properties in external galaxies
beyond MW
Abstract:
In
this talk we will try to discuss the way High Energy Physics has developed
a strategy for declaring having discovered new phenomena: we will go thro
ugh the history of HEP and see how errors can be made/avoided.
Abstract:
Progr
ess in the theoretical understanding of parton branching dynamics that occ
urs within an expanding QGP relies on detailed and fair comparisons with e
xperimental data for reconstructed jets. Such validation is only meaningfu
l when the computed object\, be it analitically or via event generation\,
accounts for the complexity of experimentally reconstructed jets. The reco
nstruction of jets in heavy ion collisions involves a\, necessarily imperf
ect\, subtraction of the large and fluctuating background: reconstructed j
ets always include background contamination.
The identification
of jet quenching effects\, that is modifications of the branching dynamics
by interaction with QGP leading to changes on jet observables\, should be
done against a baseline that accounts for possible background contaminati
on on unmodified jets. In practical terms\, jet quenching effects are only
those not present in samples of vacuum jets that have been embedded in a
realistic heavy-ion background and where subtraction has been carried out
analogously to that in the heavy ion case and as close as possible to what
is done experientally.
Using the extensively validated JEWEL ev
ent generator\, we performed an extensive survey of the sensitivity to bac
kground effects of commonly used jet observables. Further\, we have assess
ed the robustness of Machine Learning studies aimed at classifying jets ac
cording to their degree of modification by the QGP to a reference where ba
ckground contamination is accounted for.
Aiming at obtaining a j
et by jet tagger for the quenching effect in a realistic experimental sett
ing\, the previous study has gave us the opportunity to study the usage of
sophisticated architectures for the discrimination of pp and PbPb jets\,
as a proxy to discriminate quenched and unquenched jets in PbPb\, such as
transformers and energy flow networks\, accounting for background contamin
ation effects. These studies are furhter complemented by Anomaly Detection
(AD) studies using Deep Generative Learning models\, namely VAEs and beta
-VAEs attempting to identify the quenching effect as an anomaly\, again wi
th bacground contamination effects accounted for.
Abstract:
The discovery of stars orbiting very close to the su permassive black hole at the Galactic Center of the Milky Way\, Sagittariu s A*\, opened a new way to test its gravitational field and constrain the environment around it. Moreover\, data collected on stars can also be comb ined with the near horizon images taken by the Event Horizon Telescope\, p roducing the perfect laboratory to test the theory of gravity and constrai n dark matter models.
The latter represents one of the major challenges in physics\, sin ce there are several experimental observations proving its existence in th e Universe\, but none of the proposed models can be seen as conclusive. In this doctoral thesis we investigate the geodesic motion\, i.e.\, the traj ectory of a test particle in a specific gravitational field\, with the aim of understanding possible signatures of such a background.
When considering the strong f ield regime\, the geodesic equation is solved to either constrain the sign atures due to an hidden companion or study the luminosity of matter accret ed by a Schwarzschild black hole. In the context of stars at the Galactic Center\, we investigate the possibility that dark matter in the form of an ultralight field clusters around Sagittarius A* creating a cloud\, and we use the available data for star S2\, one of the closest to the Galactic C enter\, to constrain the mass of such a cloud. Moreover\, we also explore the possibility that a fifth force exists in the Universe and appears as a Yukawa-like modification to the Newtonian potential in the weak field lim it. By means of S2 data\, the intensity of such a fifth force is constrain ed at the Galactic Center.
END:VEVENT BEGIN:VEVENT SUMMARY:Quintessential Einstein-Legendre modified f(R) gravity theory DTSTART:20240404T143000Z DTEND:20240404T160000Z DTSTAMP:20240329T082743Z UID:59770cc1-8bbc-40bf-b77c-a91be809a4b2 SEQUENCE:1 CREATED:20240328T091607Z DESCRIPTION: ABSTRACT: We investigate a new formulation of f(R) gravity\, dubbed Einstein-Legendre f(R) gravity\, in which a Legendre transform is i ncluded as a dynamical term. This leads to a theory with second-order fiel d equations that describes general relativity with a self-interacting scal ar field\, without requiring the introduction of conformal frames. We find that the quadratic version of scalarized f(R) gravity reduces to general relativity with a massive scalar field\, and explore its implications for Friedmann cosmology. Our findings suggest this scalarized f(R) gravity may lead to simplified description of cosmological applications. The proposed formulation could offer a new perspective on the relationship between f(R ) gravity and scalar–tensor theories. LAST-MODIFIED:20240328T091607Z LOCATION:Sala de Seminários do DF\, Pavilhão de Física\, 2º piso URL:http://df.vps.tecnico.ulisboa.pt/eventos/quintessential-einstein-legen dre-modified-fr-gravity-theory/ X-ALT-DESC;FMTTYPE=text/html: ABSTRACT: We inves
tigate a new formulation of f(R) gravity\, dubbed Einstein-Legendre f(R) g
ravity\, in which a Legendre transform is included as a dynamical term. Th
is leads to a theory with second-order field equations that describes gene
ral relativity with a self-interacting scalar field\, without requiring th
e introduction of conformal frames.
We find that the quadratic v
ersion of scalarized f(R) gravity reduces to general relativity with a mas
sive scalar field\, and explore its implications for Friedmann cosmology.
Our findings suggest this scalarized f(R) gravity may lead to simplified d
escription of cosmological applications. The proposed formulation could of
fer a new perspective on the relationship between f(R) gravity and scalar
–tensor theories.
Abstract:
The quark-gluon plasma (QGP) is a hot and dense QCD s
tate of matter where quarks and gluons are not confined inside hadrons. It
is produced in the aftermath of ultrarelativistic heavy ion collisions (H
ICs) at the Relativistic Heavy Ion Collider and the Large Hadron Collider.
To experimentally extract the properties of QGP one often uses jets\, col
limated sprays of hadrons which result from the fragmentation of highly en
ergetic quarks and gluons.
Jets are abundantly produced in colli
der experiments and\, in HICs\, they are produced concurrently with the QG
P\, through which they have to propagate at multiple stages of their evolu
tion. In recent years\,\, the modifications of the overall energy and of t
he internal structure of in-medium jets with respect to the proton-proton
baseline\, i.e.\, without QGP production\, have been identified as a promi
sing path to perform time-differential measurements of QGP evolution.
In this presentation\, I will discuss the steps we are taking in the
direction of solidifying jets as a QGP time-imaging tool. In particular\,
I will present a recently introduced observable which aims at quantifying
jet energy loss while suppressing an important migration bias that is ine
vitable if jet comparison is made at the same reconstructed transverse mom
entum of the jet.
In doing so\, one has an unbiased estimate of
the balance between out of cone medium-induced radiation and QGP response
correlated with the jet which falls inside the jet cone. Furthermore\, I w
ill present a calculation of the spin-dependent production of a quark-anti
quark pair from an initial unpolarized gluon in an anisotropic QGP medium.
By studying how the angular and spin dependence of this production spectr
um couples to medium anisotropies\, one can gain insight on the early\, ou
t-of-equilibrium dynamics of QGP evolution.