Charge-dependent scalarization of Einstein- Euler-Heisenberg black holes

TL;DR

This paper investigates how electric charge influences the scalarization process of Einstein-Euler-Heisenberg black holes within a specific scalar-tensor theory, revealing charge-dependent scalarization phenomena and stability properties.

Contribution

It introduces a charge-dependent scalarization mechanism for EEH black holes and analyzes stability and branch structure for different charge and coupling parameters.

Findings

Scalarization occurs for specific charge and coupling sign combinations.

Stable scalarized black hole branches are identified for various charges.

Charge influences the number and stability of scalarized black hole solutions.

Abstract

Charge-dependent scalarization of the Einstein-Euler-Heisenberg (EEH) black hole is carried out in the EEH-scalar theory by introducing an exponential scalar coupling with $\alpha$ coupling constant to the Maxwell and nonlinear electrodynamic terms. The bald black hole (EEHBH) is described by mass $M$ and arbitrary magnetic charge $q$ and has a single horizon when choosing the action parameter $\mu=0.3$. The spontaneous scalarization ($\alpha^+$) of this black hole is available for charge $0<q< q_c=1.115$ and positive $\alpha$, whereas its new scalarization ($\alpha^-$) occurs for $q> q_c$ and negative $\alpha$. The former case of $q=0.5$ implies infinite branches of scalarized EEHBHs but its fundamental branch ($n=0$) is stable against radial perturbations, while the latter cases of $q=2,20$ show two stable single branches of scalarized EEHBHs.