Accelerating cosmologies in Lovelock gravity with dilaton

TL;DR

This paper explores modified Lovelock gravity with a dilaton field to model the Universe's expansion, deriving various cosmological solutions that can account for acceleration and anisotropic expansion consistent with observations.

Contribution

It provides new cosmological solutions within Lovelock gravity with dilaton, including accelerating and non-isotropizing expansions, extending previous models without dilaton or higher-order terms.

Findings

Solutions describing accelerating expansion of 3D space.

Existence of non-isotropizing cosmological solutions with matter.

Various forms of solutions including stationary, power-law, and exponential.

Abstract

For the description of the Universe expansion, compatible with observational data, a model of modified gravity - Lovelock gravity with dilaton - is investigated. D-dimensional space with 3- and (D-4)-dimensional maximally symmetric subspaces is considered. Space without matter and space with perfect fluid are under test. In various forms of the theory under way (third order without dilaton and second order - Einstein-Gauss-Bonnet gravity - with dilaton and without it) stationary, power-law, exponential and exponent-of-exponent form cosmological solutions are obtained. Last two forms include solutions which are clear to describe accelerating expansion of 3-dimensional subspace. Also there is a set of solutions describing cosmological expansion which does not tend to isotropization in the presence of matter.