English

Exponential cosmological solutions with two factor spaces in EGB model with $\Lambda = 0$ revisited

General Relativity and Quantum Cosmology 2019-07-23 v2 High Energy Physics - Theory

Abstract

We study exact cosmological solutions in DD-dimensional Einstein-Gauss-Bonnet model (with zero cosmological term) governed by two non-zero constants: α1\alpha_1 and α2\alpha_2. We deal with exponential dependence (in time) of two scale factors governed by Hubble-like parameters H>0H > 0 and hh, which correspond to factor spaces of dimensions m>2m > 2 and l>2l > 2, respectively, and D=1+m+lD = 1 + m + l. We put hHh \neq H and mH+lh0m H + l h \neq 0. We show that for α=α2/α1>0\alpha = \alpha_2/\alpha_1 > 0 there are two (real) solutions with two sets of Hubble-like parameters: (H1,h1)(H_1, h_1) and (H2,h2)(H_2, h_2), which obey: h1/H1<m/l<h2/H2<0 h_1/ H_1 < - m/l < h_2/ H_2 < 0, while for α<0\alpha < 0 the (real) solutions are absent. We prove that the cosmological solution corresponding to (H2,h2)(H_2, h_2) is stable in a class of cosmological solutions with diagonal metrics, while the solution corresponding to (H1,h1)(H_1, h_1) is unstable. We present several examples of analytical solutions, e.g. stable ones with small enough variation of the effective gravitational constant GG, for (m,l)=(9,l>2),(12,11),(11,16),(15,6)(m, l) = (9, l > 2), (12, 11), (11,16), (15, 6).

Keywords

Cite

@article{arxiv.1904.05469,
  title  = {Exponential cosmological solutions with two factor spaces in EGB model with $\Lambda = 0$ revisited},
  author = {V. D. Ivashchuk and A. A. Kobtsev},
  journal= {arXiv preprint arXiv:1904.05469},
  year   = {2019}
}

Comments

21 pages, Latex, 3 figures, revised version, Appendix is added

R2 v1 2026-06-23T08:36:09.721Z