Charged Galileon black holes

TL;DR

This paper constructs and analyzes charged black hole solutions within a specific scalar-tensor theory involving a Galileon field coupled to an Abelian gauge field, revealing new regular and dyonic black hole configurations.

Contribution

It introduces new charged black hole solutions in a Horndeski-based scalar-tensor theory, including regular horizon solutions and extensions of self-tuning black holes with dyonic charge.

Findings

Existence of regular scalar-hairy black holes with gauge fields.

Extension of self-tuning black holes to dyonic charges.

Method compatible with general shift-invariant scalar-tensor theories.

Abstract

We consider an Abelian gauge field coupled to a particular truncation of Horndeski theory. The Galileon field has translation symmetry and couples non minimally both to the metric and the gauge field. When the gauge-scalar coupling is zero the gauge field reduces to a standard Maxwell field. By taking into account the symmetries of the action, we construct charged black hole solutions. Allowing the scalar field to softly break symmetries of spacetime we construct black holes where the scalar field is regular on the black hole event horizon. Some of these solutions can be interpreted as the equivalent of Reissner-Nordstrom black holes of scalar tensor theories with a non trivial scalar field. A self tuning black hole solution found previously is extended to the presence of dyonic charge without affecting whatsoever the self tuning of a large positive cosmological constant. Finally, for a general shift invariant scalar tensor theory we demonstrate that the scalar field Ansatz and method we employ are mathematically compatible with the field equations. This opens up the possibility for novel searches of hairy black holes in a far more general setting of Horndeski theory.