Gravitational decoupling for axially symmetric systems and rotating black holes

TL;DR

This paper presents a new method using gravitational decoupling to generate rotating black holes with additional matter fields, extending classical solutions like Kerr and Kerr-Newman, and exploring their observational implications.

Contribution

It introduces a systematic approach to deform spherically symmetric solutions into hairy rotating black holes without using the Newman-Janis algorithm.

Findings

Extended Kerr and Kerr-Newman solutions with primary hair.

Rotating charged black holes can share horizons with classical solutions.

Potential observational effects due to surrounding matter around black holes.

Abstract

We introduce a systematic and direct procedure to generate hairy rotating black holes by deforming a spherically symmetric seed solution. We develop our analysis in the context of the gravitational decoupling approach, without resorting to the Newman-Janis algorithm. As examples of possible applications, we investigate how the Kerr black hole solution is modified by a surrounding fluid with conserved energy-momentum tensor. We find non-trivial extensions of the Kerr and Kerr-Newman black holes with primary hair. We prove that a rotating and charged black hole can have the same horizon as Kerr's, Schwarzschild's or Reissner-Nordstr\"om's, thus showing possible observational effects of matter around black holes.