A spin foam framework for the black-to-white hole transition

TL;DR

This paper develops a spin foam framework to describe the quantum transition of black holes into white holes, providing a non-perturbative quantum gravitational perspective on black hole end states.

Contribution

It introduces a novel spin foam approach to model the black-to-white hole transition, explicitly computing the transition amplitude within this quantum gravity formalism.

Findings

The quantum transition from black to white hole is a natural scenario.

The transition amplitude for the process is explicitly calculated.

The framework supports the idea of small black holes ending as white holes after evaporation.

Abstract

Black holes formation and evolution have been extensively studied at the classical level. However, not much is known regarding the end of their lives, a phase that requires to consider the quantum nature of the gravitational field. A black-to-white hole transition can capture the physics of this phenomenon, in particular the physics of the residual small black holes at the end of the Hawking evaporation. This work shows how the spin foam formalism is able to describe this non-perturbative phenomenon. A thorough examination of the black hole spacetime region in which quantum effects cannot be neglected indicates that the scenario in which the black hole geometry undergoes a quantum transition in a white hole geometry is natural and conservative. This quantum transition is then studied using the spin foam formalism and the resulting transition amplitude is explicitly computed.