Cosmological solutions in Einstein-Gauss-Bonnet gravity with static curved extra dimensions

TL;DR

This paper systematically investigates static extra-dimensional solutions in Einstein-Gauss-Bonnet gravity, revealing stability patterns based on curvature sign and explaining previous findings on compactification.

Contribution

It introduces a comprehensive scheme for constructing solutions with various extra dimensions and analyzes their stability, highlighting the role of curvature sign in solution stability.

Findings

Negative curvature solutions are always stable.

Positive curvature solutions are stable only within a narrow parameter range.

Negative curvature solutions do not coexist with maximally-symmetric solutions.

Abstract

In this paper we perform systematic investigation of all possible solutions with static compact extra dimensions and expanding three-dimensional subspace (``our Universe''). Unlike previous papers, we consider extra-dimensional subspace to be constant-curvature manifold with both signs of spatial curvature. We provide a scheme how to build solutions in all possible number of extra dimensions and perform stability analysis for the solutions found. Our study suggests that the solutions with negative spatial curvature of extra dimensions are always stable while those with positive curvature are stable for a narrow range of the parameters and the width of this range shrinks with growth of the number of extra dimensions. This explains why in the previous papers we detected compactification in the case of negative curvature but the case of positive curvature remained undiscovered. Another interesting feature which distinguish cases with positive and negative curvatures is that the latter do not coexist with maximally-symmetric solutions (leading to ``geometric frustration'' of a sort) while the former could -- this difference is noted and discussed.