Black Hole in a Model with Dilaton and Monopole Fields

TL;DR

This paper presents an exact, asymptotically flat black hole solution in a model with gravity, a dilaton, and a monopole field, featuring two horizons and satisfying energy conditions outside the horizon.

Contribution

It introduces a new exact black hole solution with a dilaton and monopole field, extending previous models and satisfying energy conditions.

Findings

Solution has three free parameters including monopole charge and ADM mass.

The metric has two horizons and a singularity at r=0.

The solution generalizes the GHS-GM black hole for specific parameters.

Abstract

We present an exact black hole solution in a model having besides gravity a dilaton and a monopole field. The solution has three free parameters, one of which can be identified with the monopole charge, and another with the ADM mass. The metric is asymptotically flat and has two horizons and irremovable singularity only at $r=0$. 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 the well know GHS-GM solution is obtained from our solution for certain values of its parameters.