Asymptotically flat vacuum solution for a rotating black hole in a modified gravity theory

TL;DR

This paper derives an asymptotically flat rotating black hole solution in f(R)-gravity, revealing modifications to black hole properties such as orbit radii and horizon size, and supporting the weak cosmic censorship hypothesis.

Contribution

It presents the first asymptotically flat rotating black hole solution in f(R)-gravity, extending the Kerr solution within modified gravity frameworks.

Findings

Black hole horizon and orbit radii increase with modified gravity parameter.

Black holes can spin faster than in Einstein gravity without naked singularities.

Supports the weak cosmic censorship hypothesis in modified gravity.

Abstract

The theory of f(R)-gravity is one of the theories of modified Einstein gravity. The vacuum solution, on the other hand, of the field equation is the solution for black hole geometry. We establish here an asymptotically flat rotating black hole solution in an f(R)-gravity. This essentially leads to the modified solution to the Kerr black hole. This solution exhibits the change in fundamental properties of the black hole and its geometry. It particularly shows that radii of marginally stable and bound orbits and black hole event horizon increase compared to those in Einstein gravity, depending on the modified gravity parameter. It further argues for faster spinning black holes with spin (Kerr) parameter greater than unity, without any naked singularity. This supports the weak cosmic censorship hypothesis.