# Phase Structures and Transitions of Born-Infeld Black Holes in a Grand Canonical Ensemble

## TL;DR

This paper explores the phase structures and transitions of Born-Infeld black holes under different boundary conditions, revealing diverse stability behaviors and phase transition types in a grand canonical ensemble.

## Contribution

It provides a comparative analysis of BI black holes in AdS space and a cavity, highlighting their distinct phase structures and transition characteristics.

## Key findings

- BI-AdS black holes exhibit Hawking-Page-like first order phase transitions.
- Large potentials lead to zeroth order phase transitions.
- BI black holes in a cavity show both first and second order phase transitions.

## Abstract

To make a Born-Infeld (BI) black hole thermally stable, we consider two types of boundary conditions, i.e., the asymptotically anti-de Sitter (AdS) space and a Dirichlet wall placed in the asymptotically flat space. The phase structures and transitions of these two types of BI black holes, namely BI-AdS black holes and BI black holes in a cavity, are investigated in a grand canonical ensemble, where the temperature and the potential are fixed. For BI-AdS black holes, the globally stable phases can be the thermal AdS space. For small values of the potential, there is a Hawking-Page-like first order phase transition between the BI-AdS black holes and the thermal-AdS space. However, the phase transition becomes zeroth order when the values of the potential are large enough. For BI black holes in a cavity, the globally stable phases can be a naked singularity or an extremal black hole with the horizon merging with the wall, which both are on the boundaries of the physical parameter region. The thermal flat space is never globally preferred. Besides a first order phase transition, there is a second order phase transition between the globally stable phases. Thus, it shows that the phase structures and transitions of BI black holes with these two different boundary conditions have several dissimilarities.