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SUMMARY:Quasi-local Photon Surfaces in General Spherically Symmetric Space
times
DTSTART;VALUE=DATE-TIME:20211206T232000Z
DTEND;VALUE=DATE-TIME:20211206T235000Z
DTSTAMP;VALUE=DATE-TIME:20230603T155059Z
UID:indico-contribution-6436@indico.ipmu.jp
DESCRIPTION:Speakers: Yong Song (University of Science and Technology of C
hina)\nBased on the geometry of the codimension-2 surface in general spher
ically symmetric spacetime\, we give a quasi-local definition of a photon
sphere as well as a photon surface. This new definition is the generalizat
ion of the one provided by Claudel\, Virbhadra\, and Ellis but without ref
erencing any umbilical hypersurface in the spacetime. The new definition e
ffectively excludes the photon surface in spacetime without gravity. The a
pplication of the definition to the Lemaître–Tolman–Bondi (LTB) model
of gravitational collapse reduces to a second order differential equation
problem. We find that the energy balance on the boundary of the dust ball
can provide one of the appropriate boundary conditions to this equation.
Based on this crucial investigation\, we find an analytic photon surface s
olution in the Oppenheimer– Snyder (OS) model and reasonable numerical s
olutions for the marginally bounded collapse in the LTB model. Interesting
ly\, in the OS model\, we find that the time difference between the occurr
ence of the photon surface and the event horizon is mainly determined by t
he total mass of the system but not the size or the strength of the gravit
ational field of the system.\n\nhttps://indico.ipmu.jp/event/397/contribut
ions/6436/
LOCATION:Online
URL:https://indico.ipmu.jp/event/397/contributions/6436/
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