Black holes in a swirling universe

TL;DR

This paper introduces an analytical solution in General Relativity describing a Schwarzschild black hole within a rotating universe, analyzing its physical properties, ergoregions, geodesics, and thermodynamics, and extending to the Kerr case.

Contribution

It presents a novel exact solution for a black hole in a rotating universe using a new symmetry of the Ernst equations, expanding the understanding of such configurations.

Findings

The solution is regular outside the event horizon.

It exhibits well-defined thermodynamics.

The analysis includes ergoregions and geodesic structure.

Abstract

We present a new solution in Einstein's General Relativity representing a Schwarzschild black hole immersed in a rotating universe. Such a solution is constructed analytically by means of the last unexplored Lie point symmetry of the Ernst equations for stationary and axisymmetric spacetimes. This kind of the Ehlers transformation is able to embed any given solution into a rotating background, which is not of NUT type. We analyse the physical properties, ergoregions and geodesics of the new metric, which is regular outside the event horizon and has a well defined thermodynamics. We finally consider the Kerr generalisation.