Exponential fading to white of black holes in quantum gravity

TL;DR

This paper explores a quantum gravity model suggesting black holes can decay into white holes with an exponential probability, potentially leading to observable phenomena like black stars instead of traditional black holes.

Contribution

It introduces a novel decay channel for black holes into white holes using a quantum gravity framework and calculates the associated probability distribution.

Findings

Decay probability depends only on Schwarzschild mass and a width parameter.

Probability distribution exhibits exponential decay with mean lifetime inversely proportional to mass.

Implications for black hole evolution and potential observational signatures in gravitational waves.

Abstract

Quantization of the gravitational field may allow the existence of a decay channel of black holes into white holes with an explicit time-reversal symmetry. The definition of a meaningful decay probability for this channel is studied in spherically symmetric situations. As a first nontrivial calculation, we present the functional integration over a set of geometries using a single-variable function to interpolate between black-hole and white-hole geometries in a bounded region of spacetime. This computation gives a finite result which depends only on the Schwarzschild mass and a parameter measuring the width of the interpolating region. The associated probability distribution displays an exponential decay law on the latter parameter, with a mean lifetime inversely proportional to the Schwarzschild mass. In physical terms this would imply that matter collapsing to a black hole from a finite radius bounces back elastically and instantaneously, with negligible time delay as measured by external observers. These results invite to reconsider the ultimate nature of astrophysical black holes, providing a possible mechanism for the formation of black stars instead of proper general relativistic black holes. The existence of both this decay channel and black stars can be tested in future observations of gravitational waves.