Black supernovae and black holes in non-local gravity

TL;DR

This paper explores black hole formation in non-local gravity, showing that collapse can produce event horizons with finite lifetimes, and discusses the stability and potential evaporation of these black holes.

Contribution

It provides a full spacetime solution in non-local gravity, demonstrating black hole formation with finite lifetime and analyzing their stability and relation to Hawking evaporation.

Findings

Collapse creates an event horizon in finite time

Central singularity is approached in infinite time

Black holes exhibit ghost-instability and finite lifetime

Abstract

In a previous paper, we studied the interior solution of a collapsing body in a non-local theory of gravity super-renormalizable at the quantum level. We found that the classical singularity is replaced by a bounce, after which the body starts expanding. A black hole, strictly speaking, never forms. The gravitational collapse does not create an event horizon but only an apparent one for a finite time. In this paper, we solve the equations of motion assuming that the exterior solution is static. With such an assumption, we are able to reconstruct the solution in the whole spacetime, namely in both the exterior and interior regions. Now the gravitational collapse creates an event horizon in a finite comoving time, but the central singularity is approached in an infinite time. We argue that these black holes should be unstable, providing a link between the scenarios with and without black holes. Indeed, we find a non catastrophic ghost-instability of the metric in the exterior region. Interestingly, under certain conditions, the lifetime of our black holes exactly scales as the Hawking evaporation time.