Scalarized Einstein-Maxwell-scalar black holes in anti-de Sitter spacetime

In this paper, we study spontaneous scalarization of asymptotically anti-de Sitter charged black holes in an Einstein-Maxwell-scalar model with a non-minimal coupling between the scalar and Maxwell fields. In this model, Reissner-Nordstrom-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 richer 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.

Automated summary

This paper investigates the spontaneous scalarization of asymptotically anti-de Sitter charged black holes in a specific model with non-minimal coupling, discussing the domain of existence, stability, and phase structure for both RNAdS and scalarized black hole solutions. In a micro-canonical ensemble, scalarized solutions are thermodynamically favored, but there are richer phase transitions in a canonical ensemble, including a reentrant phase transition involving RNAdS and scalarized black holes.