Dilatonic Black Holes with Gauss-Bonnet Term

TL;DR

This paper explores various black hole solutions within a superstring-inspired effective theory, analyzing their thermodynamics, stability, and evaporation behavior, revealing critical points, singularities, and potential end states of black hole evolution.

Contribution

It introduces four types of spherically symmetric black hole solutions in a superstring-derived model with a dilaton and Gauss-Bonnet term, analyzing their properties and stability.

Findings

Critical points and singular end points identified for neutral and electrically charged black holes.

Black hole temperature remains finite at critical and singular points, affecting evaporation outcomes.

Instability arises in black holes between critical and singular points, influencing their evolution.

Abstract

We discuss black holes in an effective theory derived from a superstring model, which includes a dilaton field, a gauge field and the Gauss-Bonnet term. Assuming U(1) or SU(2) symmetry for the gauge field, we find four types of spherically symmetric solutions, i.e., a neutral, an electrically charged, a magnetically charged and a ``colored'' black hole, and discuss their thermodynamical properties and fate via the Hawking evaporation process. For neutral and electrically charged black holes, we find critical point and a singular end point. Below the mass corresponding to the critical point, nosolution exists, while the curvature on the horizon diverges and anaked singularity appears at the singular point. A cusp structure in the mass-entropy diagram is found at the critical point and black holes on the branch between the critical and singular points become unstable. For magnetically charged and ``colored" black holes, the solution becomes singular just at the end point with a finite mass. Because the black hole temperature is always finite even at the critical point or the singular point, we may conclude that the evaporation process will not be stopped even at the critical point or the singular point, and the black hole will move to a dynamical evaporation phase or a naked singularity will appear.