Evolution of black holes through a nonsingular cosmological bounce

TL;DR

This paper investigates how black holes behave during a nonsingular cosmological bounce, showing that their horizons can shrink or disappear temporarily but generally persist through the bounce, with their mass remaining stable.

Contribution

It provides the first detailed nonlinear analysis of black hole evolution during a nonsingular bounce, revealing horizon dynamics and stability of black hole mass.

Findings

Black hole horizons can temporarily disappear during contraction.

Most local cosmological evolution remains unaffected by black holes.

Black holes generally survive the bounce with their initial mass.

Abstract

We study the classical dynamics of black holes during a nonsingular cosmological bounce. Taking a simple model of a nonsingular bouncing cosmology driven by the combination of a ghost and ordinary scalar field, we use nonlinear evolutions of the Einstein equations to follow rotating and non-rotating black holes of different sizes through the bounce. The violation of the null energy condition allows for a shrinking black hole event horizon and we find that for sufficiently large black holes (relative to the minimum Hubble radius) the black hole apparent horizon can disappear during the contraction phase. Despite this, we show that most of the local cosmological evolution remains largely unaffected by the presence of the black hole. We find that, independently of the black hole's initial mass, the black hole's event horizon persists throughout the bounce, and the late time dynamics consists of an expanding universe with a black hole of mass comparable to its initial value.