Obstructions on the horizon geometry from string theory corrections to Einstein gravity

TL;DR

This paper investigates how string theory corrections, specifically Gauss-Bonnet terms, restrict the horizon geometries of black holes in higher-dimensional Einstein gravity, limiting the variety of exotic black hole solutions.

Contribution

It demonstrates that Gauss-Bonnet string corrections impose severe constraints on horizon geometries, ruling out many known exotic black hole solutions with non-constant curvature horizons.

Findings

Gauss-Bonnet corrections limit horizon geometries

Most known exotic black holes are incompatible with string corrections

Constraints reduce the diversity of black hole solutions

Abstract

Higher dimensional Einstein gravity in vacuum admits static black hole solutions with an Einstein manifold of non constant curvature as a horizon. This gives a much richer family of static black holes than in four dimensional GR. However, as we show in this paper, the Gauss-Bonnet string theory correction to Einstein gravity poses severe limitations on the geometry of a horizon Einstein manifold. The additional stringy constraints rule out most of the known examples of exotic black holes with a horizon of non constant curvature.