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PHYSICS PHD DISSERTATION DEFENSE: Geoff Penington

Ph.D. Candidate:  Geoff Penington


Research Advisor:  Patrick Hayden

Date: Friday May 1, 2020
Time: 12pm
Zoom Meeting Link: https://stanford.zoom.us/j/92994370343

Zoom Meeting Password: (Email mariaf67@stanford.edu for password)

Title: Replica Wormholes, Entanglement Wedges and the Black Hole Information Paradox

Abstract: Hawking famously argued, based on semiclassical calculations, that the radiation from evaporating black holes is always perfectly thermal and contains no information about the matter that fell in. Such a result is inconsistent with the unitarity of quantum mechanics. In this defense, I will argue that a more careful replica trick calculation shows that the gravitational path integral becomes dominated at late times by saddles containing spacetime wormholes. These wormholes cause the entropy to decrease after the Page time, consistent with unitarity, and allow information to escape from the interior of the black hole. In very simple toy models, we can evaluate the path integral exactly, and see the information emerge. In more realistic black holes, the full wormhole solutions cannot be found explicitly. However, their existence, and their most important consequences, can be derived by studying the location and properties of a non-trivial ‘quantum extremal surface’ in the original Hawking solution.

May 1, 2020 - 12:00pm