Does the mass of a black hole decrease due to the accretion of phantom energy

TL;DR

This paper investigates the impact of phantom energy accretion on black hole mass, revealing that black holes may grow instead of shrink, potentially leading to violations of cosmic censorship in a phantom energy-dominated universe.

Contribution

The study provides new exact solutions showing black hole mass increase due to phantom energy, contrasting previous models that predicted mass decrease.

Findings

Black hole mass may increase with phantom energy accretion.

Black hole and cosmic horizons may coincide before the Big Rip.

Naked singularities could form, violating cosmic censorship.

Abstract

According to Babichev et al., the accretion of a phantom test fluid onto a Schwarzschild black hole will induce the mass of the black hole to decrease, however the backreaction was ignored in their calculation. Using new exact solutions describing black holes in a background Friedmann-Robertson-Walker universe, we find that the physical black hole mass may instead increase due to the accretion of phantom energy. If this is the case, and the future universe is dominated by phantom dark energy, the black hole apparent horizon and the cosmic apparent horizon will eventually coincide and, after that, the black hole singularity will become naked in finite comoving time before the Big Rip occurs, violating the Cosmic Censorship Conjecture.