Scalarization of the Reissner-Nordstr\"om black hole with higher derivative gauge field corrections

TL;DR

This paper investigates how higher derivative gauge field corrections induce scalarization in Reissner-Nordström black holes, revealing new unstable branches, overcharging possibilities, and thermodynamically favored solutions with larger entropy.

Contribution

It introduces a novel analysis of scalarization caused by higher derivative gauge corrections in Reissner-Nordström black holes, highlighting new solution branches and thermodynamic advantages.

Findings

Higher derivative corrections cause tachyonic instability leading to scalarization.

Scalarized black holes can be overcharged beyond extremality.

Solutions have larger entropy than standard Reissner-Nordström black holes.

Abstract

We discuss spontaneous scalarization of the Reissner-Nordstr\"om black hole in the presence of higher derivative gauge field corrections that arise in the context of string, as well as higher-dimensional more fundamental gravity theories. Our theory admits the Reissner-Nordstr\"om solution at the scalar vacuum of the theory ($\phi=0$) and we find that the higher order derivative gauge field correction term results in the tachyonic instability of our system once the coupling function satisfies the condition that its second derivative is positive at the scalar vacuum in the appropriate parameter space. We find that the branches do not end with an extremal black hole, rather with a singularity as indicated by the divergence of the Kretschmann scalar. The black holes can be overcharged in the sense that they may carry larger electric charge in comparison to their mass. Finally, these solutions possess larger entropy at the event horizon radius when compared to the Reissner-Nordstr\"om black hole, as well as to scalarized black holes without the higher order derivative gauge field terms, indicating in this way the thermodynamic prefer-ability of our system, when compared to existing literature, while they respect the energy conditions.