Scalarized Einstein-Born-Infeld-scalar Black Holes

TL;DR

This paper investigates spontaneous scalarization in Einstein-Born-Infeld-scalar black holes, revealing two types of solutions and significant differences from models with Maxwell electrodynamics, especially regarding solution branches and their properties.

Contribution

It introduces the EBIS model with non-minimal coupling of Born-Infeld electrodynamics to scalar fields, identifying new scalarized black hole solutions and their bifurcation and stability properties.

Findings

Two types of scalarized black hole solutions identified.

Significant differences between EBIS and EMS models in Schwarzschild-like solutions.

Existence of disconnected scalarized solution branches with complex bifurcation behavior.

Abstract

The phenomenon of spontaneous scalarization of Reissner-Nordstr\"{o}m (RN) black holes has recently been found in an Einstein-Maxwell-scalar (EMS) model due to a non-minimal coupling between the scalar and Maxwell fields. Non-linear electrodynamics, e.g., Born-Infeld (BI) electrodynamics, generalizes Maxwell's theory in the strong field regime. Non-minimally coupling the BI field to the scalar field, we study spontaneous scalarization of an Einstein-Born-Infeld-scalar (EBIS) model in this paper. It shows that there are two types of scalarized black hole solutions, i.e., scalarized RN-like and Schwarzschild-like solutions. Although the behavior of scalarized RN-like solutions in the EBIS model is quite similar to that of scalarize solutions in the EMS model, we find that there exist significant differences between scalarized Schwarzschild-like solutions in the EBIS model and scalarized solutions in the EMS model. In particular, the domain of existence of scalarized Schwarzschild-like solutions possesses a certain region, which is composed of two branches. The branch of larger horizon area is a family of disconnected scalarized solutions, which do not bifurcate from scalar-free black holes. However, the branch of smaller horizon area may or may not bifurcate from scalar-free black holes depending on the parameters. Additionally, these two branches of scalarized solutions can be both entropically disfavored over comparable scalar-free black holes in some parameter region.