Hairy black holes by gravitational decoupling

TL;DR

This paper explores black holes with hair using gravitational decoupling, revealing new solutions that satisfy energy conditions and extend classical black hole models like Reissner-Nordstrom.

Contribution

It introduces a novel method to generate hairy black hole solutions via gravitational decoupling, bypassing traditional no-hair theorems.

Findings

Trivial deformations of Schwarzschild preserve energy conditions.

Discovered primary hair associated with charge increases entropy.

Extended Reissner-Nordstrom black hole with a simple horizon.

Abstract

Black holes with hair represented by generic fields surrounding the central source of the vacuum Schwarzschild metric are examined under the minimal set of requirements consisting of i) the existence of a well defined event horizon and ii) the strong or dominant energy condition for the hair outside the horizon. We develop our analysis by means of the gravitational decoupling approach. We find that trivial deformations of the seed Schwarzschild vacuum preserve the energy conditions and provide a new mechanism to evade the no-hair theorem based on a primary hair associated with the charge generating these transformations. Under the above conditions i) and ii), this charge consistently increases the entropy from the minimum value given by the Schwarzschild geometry. As a direct application, we find a non-trivial extension of the Reissner-Nordstrom black hole showing a surprisingly simple horizon. Finally, the non-linear electrodynamics generating this new solution is fully specified.