Speaker: Samir Mathur (Ohio State)
Title: The story of the information paradox
Abstract: In 1975 Hawking argued that black hole evaporation would lead to a loss of unitarity in quantum theory. The small corrections theorem made Hawking’s argument into a precise statement: if semiclassical physics hold to leading order in any gently curved region of spacetime, then there can be no resolution to the paradox. In string theory, whenever people have been able to construct microstates explicutly, the states turned out to be horizon sized objects (fuzzballs) with no horizon; such a structure of microstates resolves the information paradox since their is no pair creation at a vacuum horizon. There have been a set of parallel attempts to resolve the paradox (with ideas involving wormholes, islands etc) where the horizon is smooth in some leading approximation. An analysis of such models however indicated that in each case the exact quantum gravity theory would either have to be nonunitary or to have dynamics at infinity that is conflict with usual low energy physics in the lab.