High Energy Physics Seminar
Speaker: Jason Pollack, University of British Columbia
Title: Black Holes and the Hilbert Space of Quantum Gravity
Refreshments available at 1:30 pm.
Date: Tue, 10 Apr 2018, 1:45 pm – 2:45 pm
Location: 1400 BPS Bldg.
We discuss the branching structure of the quantum-gravitational wave function that describes the evaporation of a black hole. A global wave function that initially describes a classical Schwarzschild geometry is continually decohered into distinct semi classical branches by the emission of Hawking radiation. The laws of quantum mechanics dictate that the wave function evolves unitarily, but this unitary evolution is only manifest when considering the global description of the wave function: it is not implemented by time evolution on a single semi classical branch. Conversely, geometric notions like the position or smoothness of a horizon only make sense on the level of individual branches. We consider the implications of this picture for probes of black holes by classical observers in definite geometries, like those involved in the AMPS construction leading to the "firewall paradox." We argue that individual branches can describe semi classical geometries free of firewalls, even as the global wave function evolves unitarily.