Spontaneous scalarization of charged black holes in the Scalar-Vector-Tensor theory

TL;DR

This paper explores how charged black holes can spontaneously develop scalar fields through specific couplings in a scalar-vector-tensor theory, leading to new stable scalarized black hole solutions.

Contribution

It introduces a novel mechanism for scalarization of charged black holes via coupling to electromagnetic and curvature tensors, and analyzes their stability.

Findings

Scalarization occurs via tachyonic instability of scalar fields around RN black holes.

Stable scalarized black hole solutions are constructed and analyzed.

The model demonstrates conditions under which scalarization is triggered and maintained.

Abstract

We present spontaneous scalarization of charged black holes (BHs) which is induced by the coupling of the scalar field to the electromagnetic field strength and the double-dual Riemann tensor $L^{\mu\nu\alpha\beta}F_{\mu\nu}F_{\alpha\beta}$ in a scalar-vector-tensor theory. In our model, the scalarization can be realized under the curved background with a non-trivial electromagnetic field, such as Reissner-Nordstr$\ddot{\rm o}$m Black Holes (RN BHs). Firstly, we investigate the stability of the constant scalar field around RN BHs in the model, and show that the scalar field can suffer a tachyonic instability. Secondly, the bound state solution of the test scalar field around a RN BH and its stability are discussed. Finally, we construct scalarized BH solutions, and investigate their stability.