Scalar hairy black holes and solitons in a gravitating Goldstone model

TL;DR

This paper investigates scalar hairy black holes and solitons within a gravitating Goldstone model, revealing regular particle-like solutions and extremal black holes in a four-dimensional setting.

Contribution

It introduces new static, spherically symmetric solutions in Einstein-Goldstone theory, including regularized monopoles and extremal black holes without additional matter fields.

Findings

Existence of finite-mass, regular monopole-like solutions

Discovery of extremal black holes with scalar fields only

Solutions approach Minkowski spacetime at infinity

Abstract

We study black hole solutions of Einstein gravity coupled to a specific global symmetry breaking Goldstone model described by an O(3) isovector scalar field in four spacetime dimensions. Our configurations are static and spherically symmetric, approaching at infinity a Minkowski spacetime background. A set of globally regular, particle-like solutions are found in the limit of vanishing event horizon radius. These configurations can be viewed as 'regularised' global monopoles, since their mass is finite and the spacetime geometry has no deficit angle. As an unusual feature, we notice the existence of extremal black holes in this model defined in terms of gravity and scalar fields only.