Stable exponential cosmological solutions with zero variation of G and three different Hubble-like parameters in the Einstein\u2013Gauss\u2013Bonnet model with a Lambda -term

Abstract

We consider a D-dimensional gravitational model with a Gauss–Bonnet term and the cosmological term Lambda . We restrict the metrics to diagonal cosmological ones and find for certain Lambda a class of solutions with exponential time dependence of three scale factors, governed by three non-coinciding Hubble-like parameters H >0, h_1 and h_2, corresponding to factor spaces of dimensions m > 2, k_1 > 1 and k_2 > 1, respectively, with k_1 ne k_2 and D = 1 + m + k_1 + k_2. Any of these solutions describes an exponential expansion of 3d subspace with Hubble parameter H and zero variation of the effective gravitational constant G. We prove the stability of these solutions in a class of cosmological solutions with diagonal metrics.