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SUMMARY:Breaking Buchdahl: Ultracompact stars in semiclassical gravity
DTSTART:20241121T143000Z
DTEND:20241121T160000Z
DTSTAMP:20260906T120854Z
UID:185295e6-db95-43ba-8734-8705f797b12c
SEQUENCE:1
CREATED:20241115T154837Z
DESCRIPTION: The Buchdahl theorem imposes a bound on the maximum compactne
 ss that stars in equilibrium can achieve in general relativity. This bound
  is one of the theoretical motivations behind the belief that the dark and
  compact objects that we observe must correspond to black holes. In this t
 alk\, I will revise the hypotheses behind the Buchdahl theorem and address
  the consequences of individually relaxing its assumptions.In particular\,
  if the energy density of the stellar fluid is allowed to become negative\
 , it is possible to obtain regular stars as compact as black holes. To con
 clude\, I will show how similar models of black hole mimickers are found w
 ithin semiclassical theories of gravity that consider the backreaction eff
 ects of the quantum vacuum. 
LAST-MODIFIED:20241115T154837Z
LOCATION:DF Seminar Room (2-8.3)\, 2nd floor of Physics Building
URL:http://df.vps.tecnico.ulisboa.pt/en/events/breaking-buchdahl-ultracomp
 act-stars-in-semiclassical-gravity/
X-ALT-DESC;FMTTYPE=text/html:<p data-block-key="wti34"> The Buchdahl theor
 em imposes a bound on the maximum compactness that stars in equilibrium ca
 n achieve in general relativity. This bound is one of the theoretical moti
 vations behind the belief that the dark and compact objects that we observ
 e must correspond to black holes. In this talk\, I will revise the hypothe
 ses behind the Buchdahl theorem and address the consequences of individual
 ly relaxing its assumptions.<br/><br/><br/>In particular\, if the energy d
 ensity of the stellar fluid is allowed to become negative\, it is possible
  to obtain regular stars as compact as black holes. To conclude\, I will s
 how how similar models of black hole mimickers are found within semiclassi
 cal theories of gravity that consider the backreaction effects of the quan
 tum vacuum. </p>
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