From black holes to white holes: a quantum gravitational, symmetric bounce

TL;DR

This paper explores how quantum gravity effects can produce a symmetric bounce from black hole to white hole, addressing asymmetries in previous models by modifying loop quantization procedures.

Contribution

It introduces a method to achieve symmetric black hole-white hole bounces by adjusting quantization ambiguities in loop quantum gravity.

Findings

Symmetric bounce conditions can be satisfied with slight modifications in loop construction.

Quantization ambiguities can lead to identical mass black hole and white hole after bounce.

Modified quantization approaches can resolve or alter key features of singularity physics.

Abstract

Recently a consistent non-perturbative quantization of the Schwarzschild interior resulting in a bounce from black hole to white hole geometry has been obtained by loop quantizing the Kantowski-Sachs vacuum spacetime. As in other spacetimes where the singularity is dominated by the Weyl part of the spacetime curvature, the structure of the singularity is highly anisotropic in the Kantowski-Sachs vacuum spacetime. As a result the bounce turns out to be in general asymmetric creating a large mass difference between the parent black hole and the child white hole. In this manuscript, we investigate under what circumstances a symmetric bounce scenario can be constructed in the above quantization. Using the setting of Dirac observables and geometric clocks we obtain a symmetric bounce condition which can be satisfied by a slight modification in the construction of loops over which holonomies are considered in the quantization procedure. These modifications can be viewed as quantization ambiguities, and are demonstrated in three different flavors which all lead to a non-singular black to white hole transition with identical masses. Our results show that quantization ambiguities can mitigate or even qualitatively change some key features of physics of singularity resolution. Further, these results are potentially helpful in motivating and constructing symmetric black to white hole transition scenarios.