Resolution of cosmological singularity in Hořava-Lifshitz cosmology

Abstract

The standard ΛCDM model leaves a number of issues unaddressed, one of the most important ones being the problem of initial singularity where general relativity breaks down. Solving that problem usually requires modifications of general relativity. However, there appeared the Hořava-Lifshitz (HL) theory of gravity, in which equations governing cosmological evolution include a new term scaling similarly as dark radiation in the usual Friedmann equations, enabling a bounce of the universe instead of initial singularity. This review describes past works on a stability of such a bounce in different formulations of HL theory, initial detailed balance scenario and further projectable versions containing higher than quadratic term to the original action.