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SPEAKER: Sergey Sibiryakov (CERN)

ABSTRACT: I will describe a semiclassical method to calculate S–matrix elements for two–stage gravitational transitions involving matter collapse into a black hole and evaporation of the latter. The method consistently incorporates back–reaction of the collapsing and emitted quanta on the metric. I will illustrate the method in several toy models describing spherical self–gravitating shells in asymptotically flat and AdS space–times. The shells are found to reflect via the above collapse–evaporation process with probability exp(−B), where B is the Bekenstein–Hawking entropy of the intermediate black hole. This is consistent with interpretation of exp(B) as the number of black hole states. Our semiclassical method opens a new systematic approach to the gravitational S–matrix in the non–perturbative regime.