Events

Constraints on multi-scalar models

Tue, 29 Sep 2026 09:49:50 +0000

Monday, 12th of October, 2026 from 2 p.m. to 4 p.m.

Sala P3 (Piso 1 do Pavilhão de Matemática) do IST

The Standard Model of particle physics is one of the most successful theories ever developed. Although the Standard Model provides an accurate description of known elementary particles and their interactions, it leaves several fundamental questions unanswered, including the origin of the baryon asymmetry of the Universe, the nature of Dark Matter, and the mechanism responsible for generating neutrino masses. These shortcomings provide strong motivation for considering extensions of the Standard Model.

In the first part of this work, we present a comprehensive study of perturbative unitarity bounds in the gauge-scalar sectors of models containing additional scalar doublets, neutral singlets, or charged singlets. Such scalar sectors arise naturally in many Beyond the Standard Model scenarios and are particularly common in theories that address the dark matter problem.

We derive a complete classification of these models and identify a minimal set of scattering matrices that contains all the information required to determine …

The simple geometry of tetraquark resonances: all-charm ccc⁻c⁻ 2⁺⁺ cases

Fri, 09 Oct 2026 10:27:53 +0000

Wednesday, 14th of October, 2026 from 2:30 p.m. to 4 p.m.

DF Seminar Room (2-8.3), 2nd floor of Physics Building

Recently, many tetraquarks resonances have been foundexperimentally. However the resonances high in the spectrum arepuzzling. A priori these resonances could be much wider, because theycan freely couple to meson-meson channels with the same quantumnumbers, and then it is debatable if they are real tetraquarks ormeson-meson molecules.

We solve the puzzle with a geometricprinciple, explaining why the real tetraquarks are narrower thanexpected. We apply the Resonating Group Method, including aGeneralized Eigenvalue Problem, to compute the decay widths oftetraquark resonances in pairs of mesons.

We utilize graphical rules,enabling simple and general results to be derived. Our case study is thecomparatively simpler family of all-charm 2⁺⁺ tetraquarks observed bythe CMS and LHCb collaborations at CERN.

Biomedical Optics & the Value of Quantum Level Imaging in Medicine

Tue, 06 Oct 2026 14:41:55 +0000

Thursday, 22nd of October, 2026 from 4 p.m. to 6 p.m.

Salão Nobre Pav. Central, Campus Alameda, IST

Optics is the single largest technology sector in medicine today, with successes broadly across nearly all medical specialties, especially in point-of-care, homecare and as diagnostic detector components. Advances in camera technology have had an enormous influence, especially in areas such as robotic surgery, advanced displays, and molecular sensing.

There is a significant potential opportunity in monitoring technologies and advances in sensors. In particular, quantum-level sensors that read out single-photon events per pixel have transformed x-ray imaging and radiation Cherenkov imaging, and have important value for features such as depth sensing or lifetime-based imaging.

The example of developing Cherenkov imaging to visualize radiation dose in humans undergoing radiotherapy will be reviewed, with technical innovations, entrepreneurial development into a successful medical device, and future prospects for advancement.

Structural Order, Crystallinity, and Processing Effects in Organic Semiconducting Systems

Fri, 02 Oct 2026 08:48:58 +0000

Friday, 13th of November, 2026 from 9:30 a.m. to noon

Online

External link

Organic photovoltaic devices have attracted significant interest as lightweight, flexible, and solution-processable renewable-energy technologies. Their performance is strongly influenced by the morphological organization of the active layer, which affects charge photogeneration, transport, recombination, and collection processes. Understanding how specific structural and processing-related characteristics influence device behavior therefore remains an important topic within organic electronics.

This thesis investigates the influence of highly ordered interfaces, crystallinity, and processinginduced morphological modifications on the optoelectronic behavior of organic semiconducting systems through the study of deliberately simplified and well-defined model structures. In this context, three complementary research topics were investigated. The first research topic investigated the influence of crystal-crystal interface formation in highly ordered rubrene-based systems, revealing enhanced conductivity and charge transport associated with crystalline interfacial effects.

The second study explored the incorporation of a rubrene single-crystal donor within planar heterojunction organic solar cells, demonstrating efficient photovoltaic generation at crystalline donor/acceptor interfaces and providing insight …

Fifth Forces across Cosmic Scales: From Primordial Perturbations to Compact Stars

Wed, 30 Sep 2026 14:40:26 +0000

Friday, 20th of November, 2026 from 2 p.m. to 4 p.m.

Anfiteatro PA-3 (Piso -1 do Pavilhão de Matemática) do IST

Scalar fields coupled to matter mediating fifth-force interactions are ubiquitous in extensions of General Relativity. Reconciling their cosmological relevance with local gravity constraints requires either a weak coupling or a screening mechanism suppressing the force in dense environments.

This thesis investigates scalar-mediated fifth forces across two regimes: the unscreened early universe and the screened interiors of compact stars. In the cosmological regime, we study Early Coupled Quintessence, a model where a light scalar field mediates a fifth force stronger than gravity between dark matter particles during radiation domination, enhancing density perturbation growth with a characteristic goldenratio rate.

We implement the corresponding background and perturbation equations in the CLASS Boltzmann code and perform the first Markov chain Monte Carlo analysis of its parameter space, combining cosmic microwave background, supernovae, baryon acoustic oscillation, and big bang nucleosynthesis data. We confirm and quantify a fundamental degeneracy between the coupling strength and the redshift …