Scalarized Einstein-Born-Infeld black holes

The phenomenon of spontaneous scalarization of Reissner-Nordstrom (RN) black holes has recently been found in an Einstein-Maxwell-scalar (EMS) model due to a nonminimal coupling between the scalar and Maxwell fields. Nonlinear electrodynamics, e.g., Born-Infeld (BI) electrodynamics, generalizes Maxwell's theory in the strong field regime. Nonminimally 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 scalarized 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.

Automated summary

This study explores the phenomenon of spontaneous scalarization in the EBIS model, revealing two types of scalarized black hole solutions: scalarized RN-like and scalarized Schwarzschild-like solutions. Contrary to the EMS model, the behavior of scalarized solutions in the EBIS model shows significant differences, particularly in the domain of existence and entropy of scalarized Schwarzschild-like solutions.