Super-entropic black hole with Immirzi hair

TL;DR

This paper presents an analytic solution for asymptotically Anti-de Sitter black holes with hyperbolic horizons in f(R) gravity with a dynamical Immirzi field, revealing super-entropic behavior and modified entropy laws.

Contribution

It introduces a new analytic black hole solution with Immirzi hair in f(R) gravity, showing how the Immirzi field affects entropy and thermodynamics.

Findings

Black holes exhibit scalar hair depending on Immirzi field behavior.

The Immirzi field modifies the black hole entropy law.

The solution violates the reverse isoperimetric inequality, indicating super-entropic nature.

Abstract

In the context of f(R) generalizations to the Holst action, endowed with a dynamical Immirzi field, we derive an analytic solution describing asymptotically Anti-de Sitter black holes with hyperbolic horizon. These exhibit a scalar hair of the second kind, which ultimately depends on the Immirzi field radial behaviour. In particular, we show how the Immirzi field modifies the usual entropy law associated to the black hole. We also verify that the Immirzi field boils down to a constant value in the asymptotic region, thus restoring the standard Loop Quantum Gravity picture. We finally prove the violation of the reverse isoperimetric inequality, resulting in the super-entropic nature of the black hole, and we discuss in detail the thermodynamic stability of the solution.