Black Hole in a Model with Dilaton and Monopole Fields II

TL;DR

This paper presents an exact, asymptotically flat black hole solution in a dilaton-monopole field model, featuring two horizons, a singularity at the center, and satisfying energy conditions, with implications for the no hair conjecture.

Contribution

It introduces a new exact black hole solution with monopole and dilaton fields, extending previous models and revealing additional symmetries and conserved charges.

Findings

Black hole has two horizons and a singularity at r=0.

Solution satisfies dominant and strong energy conditions outside the external horizon.

Reformulated model with two monopole fields shows an additional symmetry and conserved dilaton charge.

Abstract

We present an exact black hole solution in a model having besides gravity a dilaton and a monopole field, which is a generalization of a black hole solution we have found. The new solution, as the previous one, has three free parameters, one of which can be identified with the monopole charge, and another with the ADM mass. Its metric is asymptotically flat, has two horizon, irremovable singularity only at $r=0$, and the dilaton field is singular only at $r=0$. The dominant and the strong energy condition are satisfied outside and on the external horizon. According to a formulation of the no hair conjecture the solution is "hairy". Also a reformulation of the model with two monopole fields is given, which results in the appearance of an additional symmetry and therefore in the appearance of a conserved dilaton charge.