Spontaneous scalarization of regular Hayward black holes in Einstein-nonlinear electromagnetic-scalar gravity

TL;DR

This paper investigates the spontaneous scalarization of Hayward black holes within Einstein-nonlinear electromagnetic-scalar gravity, revealing stable scalarized black hole solutions with potential observational relevance.

Contribution

It introduces new scalarized charged black hole solutions with quadratic and exponential couplings, analyzing their stability and classification by excitation number.

Findings

Stable n=0 black hole branch identified

Scalarized black holes characterized by coupling types

Potential for observational implications of stable solutions

Abstract

In this paper, we discuss the spontaneous scalarization of Hayward black holes in Einstein-nonlinear electromagnetic-scalar gravity. Taking into account the tachyonic instability, we obtain scalarized charged black holes (SCBHs) with quadratic (1-$\alpha\varphi^2$) and exponential ($e^{-\alpha \varphi^2}$) couplings, respectively. Moreover, these SCBHs can be labelled by the number of $n = 0, 1, 2,...$, where $n = 0$ is called the fundamental black hole and $n = 1, 2,...$ denote the $n$-excited black holes. We recover that the $n = 0$ branch for both couplings is stable against radial perturbations. This stability shows that this branch can be used for further observational implications.