Spontaneous scalarization of Bardeen black holes

TL;DR

This paper investigates the spontaneous scalarization of Bardeen black holes, revealing stable scalarized charged black hole branches with potential observational relevance due to their stability against radial perturbations.

Contribution

It demonstrates the existence and stability of scalarized Bardeen black holes with magnetic charge, expanding understanding of black hole scalarization phenomena.

Findings

Infinite branches of scalarized black holes with magnetic charge g.

The n=0 branch is stable against radial perturbations.

Scalarized branches exist above a certain coupling threshold lpha_{n=0}(g).

Abstract

We study the spontaneous scalarization of Bardeen black holes, whose tachyonic instability triggers the formation of scalarized charged black holes (SCBHs). In this case, we find infinite ($n=0,1,2,\cdots$) branches of SCBHs with magnetic charge $g$. The $n = 0$ branch of SCBHs can be found for the coupling parameter $\alpha \geq \alpha_{n=0}(g)$ with both quadratic (1-$\alpha \varphi^2$) and exponential ($e^{-\alpha \varphi^2}$) couplings, where $\alpha_{n=0}(g)$ represents the threshold of tachyonic instability for the Bardeen black holes. Furthermore, it is shown 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.