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SUMMARY:Piotr Chrusciel (University of Wien)
DTSTART:20200428T173000Z
DTEND:20200428T183000Z
DTSTAMP:20260404T094341Z
UID:BHIColloq/1
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/BHICo
 lloq/1/">Mass\, and its positivity?\, for solutions of Einstein equations 
 with negative cosmological constant.</a>\nby Piotr Chrusciel (University o
 f Wien) as part of BHI Colloquium\n\n\nAbstract\nI will review the notion 
 of mass for solutions of vacuum Einstein equations with negative cosmologi
 cal constant\, discuss some standard examples\, and outline the proof of p
 ositivity for solutions with spherical topology at infinity.\n
LOCATION:https://stable.researchseminars.org/talk/BHIColloq/1/
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BEGIN:VEVENT
SUMMARY:Martin Lesourd (BHI\, Harvard)
DTSTART:20200512T173000Z
DTEND:20200512T183000Z
DTSTAMP:20260404T094341Z
UID:BHIColloq/2
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/BHICo
 lloq/2/">How Do Black Holes Form?</a>\nby Martin Lesourd (BHI\, Harvard) a
 s part of BHI Colloquium\n\n\nAbstract\nMathematical General Relativity is
  held together by a couple of deep conjectures. Many mathematicians like t
 o think that by proving these (or finding counterexamples)\, they will fin
 ally be able to underpin (or challenge) the beliefs that Physicists and As
 trophysicists have held for decades. Arguably the grandest such example is
  the ''Final State Conjecture'': generic vacuum spacetimes undergoing grav
 itational collapse will eventually resemble the Kerr solution in their ext
 erior. At present\, there is not a single example of this conjecture\, nor
  a single vacuum spacetime with a complete future asymptotic region descri
 bing black hole formation. I will review what is known\, and describe some
  work (still in progress) with Athanasiou in this direction.\n
LOCATION:https://stable.researchseminars.org/talk/BHIColloq/2/
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SUMMARY:Frederic Vincent (Paris Meudon Observatory)
DTSTART:20200512T173000Z
DTEND:20200512T183000Z
DTSTAMP:20260404T094341Z
UID:BHIColloq/3
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/BHICo
 lloq/3/">What can we infer from black hole images?</a>\nby Frederic Vincen
 t (Paris Meudon Observatory) as part of BHI Colloquium\n\n\nAbstract\nThe 
 recent Event Horizon Telescope (EHT) millimeter image of the vicinity of t
 he supermassive compact object M87* at the center of the galaxy M87 is a b
 reakthrough. It is important to investigate what can and what cannot be in
 ferred from such images. In this talk I will discuss a simple geometric mo
 del of the region of the accretion flow immediately surrounding M87*. I wi
 ll use this model to discuss the highly-lensed features of EHT-like images
 \, often loosely referred to as the "photon ring". I will discuss whether 
 such features can be used as clean probes of the nature of the underlying 
 spacetime. I will also discuss various EHT-like images of M87*\, assuming 
 this object is various kinds of compact alternatives to the standard black
  hole. This will allow discussing to what extent can EHT-like images help 
 constrain the nature of the compact objects at the center of M87 or our Mi
 lky Way.\n
LOCATION:https://stable.researchseminars.org/talk/BHIColloq/3/
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