Speaker: Yasutaka Koga (Rikkyo University)

Title: Photon surface and relevant phenomena

Abstract:

Photon surface is a geometrical object which generalizes the photon sphere of Schwarzschild spacetime. Due to its geometrical features, there are interesting phenomena concerning the photon surface. In this talk, after reviewing a photon surface and its stability, we see two theoretical phenomena in the following.

"SP/PS correspondence":

In analysis of accretion and outflow of fluid, the existence of the sonic point (SP) plays a key role for finding physical solutions. If the matter is radiation fluid, there is a one-to-one correspondence between the sonic points and photon surfaces(PS) of the spacetime.

"Photon surface as a wormhole throat":

Wormhole spacetime is constructed by truncating two spacetimes at some boundaries and sewing them together along the boundaries. The sewn boundary is called a throat. Such a wormhole spacetime is said to be a solution of Einstein equation if Israel's junction conditions are satisfied with an adequate matter distribution on the throat. If the throat with the matter distribution is a pure tension brane, the corresponding boundaries of the original spacetimes must be photon surfaces.

Room: Sala de Reuniões e Seminários (2nd Floor of physics building)