Models for the nonsingular transition of an evaporating black hole into a white hole

Understand

There have been a number of suggestions that the r = 0 singularity of a spherically symmetric (uncharged) evaporating black hole can be circumvented by a quantum transition to a white hole, which eventually releases all trapped quantum information, consistent with overall unitary evolution of the quantum fields.

• Some of these scenarios rely on loop quantum gravity to impose a minimum area of two-spheres, but are quite vague on how to deal with black hole evaporation, particularly its endpoint.
• In this paper I present a rather complete toy model for the evolution of the geometry and the effective stress-energy tensor derived from the geometry via the classical Einstein equations.
• Modifications of the Schwarzschild geometry once the formation of the black hole is complete are very small outside regions of high curvature, and the curvature never becomes super-Planckian.