Cosmologically Coupled Black Holes with Regular Horizons

TL;DR

This paper derives the most general exact solution for Einstein's gravity with anisotropic fluids, embedding static black holes in arbitrary FLRW cosmologies without singular horizons, advancing understanding of cosmological black hole models.

Contribution

It provides the first fully backreacted, regular cosmological embedding of black holes in arbitrary FLRW universes, including a novel regular cosmological extension of Schwarzschild black holes.

Findings

Solution is free of curvature singularities at the horizon.

Introduces a new regular cosmological black hole solution.

Demonstrates backreaction effects on cosmological dynamics.

Abstract

We present the most general and exact solution of Einstein's gravity sourced by an anisotropic fluid describing the cosmological embedding (CE) of a static and spherically-symmetric object, including black holes (BHs) or exotic compact objects, without radial energy influx and in an arbitrary Friedmann-Lema\^itre-Robertson-Walker (FLRW) cosmology. This is done fully considering backreaction of the local geometry on the cosmological dynamics. Our solution is free of curvature singularities at the would-be BH event horizon, thus solving a main issue of the CE of BH solutions proposed so far. As a byproduct, we derive a new CE of the Schwarzschild BH - distinct from McVitties's original proposal - that is regular everywhere except at the central singularity.