Scalarized Einstein-Maxwell-scalar Black Holes in Anti-de Sitter Spacetime

TL;DR

This paper explores the spontaneous scalarization of charged anti-de Sitter black holes within the Einstein-Maxwell-scalar framework, revealing new phase transitions and stability properties of scalarized solutions compared to traditional black holes.

Contribution

It introduces the study of scalarized black holes in AdS spacetime with a non-minimal coupling, analyzing their stability, phase structure, and thermodynamic preferences, including reentrant phase transitions.

Findings

Scalarized black holes are thermodynamically preferred in micro-canonical ensemble.

Reentrant phase transitions occur between RNAdS and scalarized black holes.

Rich phase structure with zeroth- and second-order phase transitions.

Abstract

In this paper, we study spontaneous scalarization of asymptotically anti-de Sitter charged black holes in the Einstein-Maxwell-scalar model with a non-minimal coupling between the scalar and Maxwell fields. In this model, Reissner-Nordstr\"om-AdS (RNAdS) black holes are scalar-free black hole solutions, and may induce scalarized black holes due to the presence of a tachyonic instability of the scalar field near the event horizon. For RNAdS and scalarized black hole solutions, we investigate the domain of existence, perturbative stability against spherical perturbations and phase structure. In a micro-canonical ensemble, scalarized solutions are always thermodynamically preferred over RNAdS black holes. However, the system has much rich phase structure and phase transitions in a canonical ensemble. In particular, we report a RNAdS BH/scalarized BH/RNAdS BH reentrant phase transition, which is composed of a zeroth-order phase transition and a second-order one.