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BEGIN:VEVENT
SUMMARY:Breaking Buchdahl: Ultracompact stars in semiclassical gravity
DTSTART:20241121T143000Z
DTEND:20241121T160000Z
DTSTAMP:20260809T120045Z
UID:185295e6-db95-43ba-8734-8705f797b12c
SEQUENCE:2
CREATED:20241115T154852Z
DESCRIPTION:The Buchdahl theorem imposes a bound on the maximum compactnes
 s 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 ta
 lk\, 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 conc
 lude\, I will show how similar models of black hole mimickers are found wi
 thin semiclassical theories of gravity that consider the backreaction effe
 cts of the quantum vacuum.
LAST-MODIFIED:20241115T154951Z
LOCATION:Sala de Seminários do DF\,  Pavilhão de Física\, 2º piso
URL:http://df.vps.tecnico.ulisboa.pt/pt/eventos/breaking-buchdahl-ultracom
 pact-stars-in-semiclassical-gravity/
X-ALT-DESC;FMTTYPE=text/html:<p data-block-key="wti34">The Buchdahl theore
 m imposes a bound on the maximum compactness that stars in equilibrium can
  achieve in general relativity. This bound is one of the theoretical motiv
 ations behind the belief that the dark and compact objects that we observe
  must correspond to black holes. In this talk\, I will revise the hypothes
 es behind the Buchdahl theorem and address the consequences of individuall
 y relaxing its assumptions.<br/><br/><br/>In particular\, if the energy de
 nsity 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 sh
 ow how similar models of black hole mimickers are found within semiclassic
 al theories of gravity that consider the backreaction effects of the quant
 um vacuum.</p>
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