Enhanced Instability of de Sitter Space in Einstein-Gauss-Bonnet Gravity

TL;DR

Adding a Gauss-Bonnet term to Einstein's gravity significantly increases the instability of de Sitter space by promoting black hole nucleation, with stability bounds influenced by string theory parameters.

Contribution

This paper demonstrates how the Gauss-Bonnet term enhances de Sitter instability and establishes a stability bound related to string theory effective actions.

Findings

Gauss-Bonnet term increases black hole nucleation rate in de Sitter space.

Stability bound on de Sitter curvature depends on Gauss-Bonnet coefficient.

Maximum de Sitter curvature is lower than Planck scale in string theory context.

Abstract

We show that the addition of a topological Gauss-Bonnet term to the gravitational action can greatly increase the instability of four-dimensional de Sitter space, by favoring the nucleation of black holes. The pair-production rate given by the Euclidean action for the instanton takes the form exp(Delta S) where S is the entropy in Einstein-Gauss-Bonnet theory. The coefficient of the Gauss-Bonnet term in the action sets a stability bound on the curvature of empty de Sitter space. For that coefficient in the low-energy effective action of heterotic string theory, the maximal curvature of de Sitter space is in general much lower than the Planck scale.