Splitting Into Two Isotropic Subspaces as a Result of Cosmological Evolution in Einstein—Gauss—Bonnet Gravity

Abstract

We consider numerically the dynamics of a flat anisotropic Universe in Einstein—Gauss—Bonnet gravity with positive Λ in dimensions 5 + 1 and 6 + 1. We identify three possible outcomes of the evolution, one singular and two nonsingular ones. The first nonsingular outcome is oscillatory. The second one is the known exponential solution. Its simplest version is the isotropic de Sitter solution. In Gauss—Bonnet cosmology there also exist anisotropic exponential solutions. When an exponential solution being a result of cosmological evolution has two different Hubble parameters, the evolution leads from an initially totally anisotropic stage to a warped product of two isotropic subspaces. We show that such a type of evolution is rather typical and possible even in the case where the de Sitter solution also exists.