An Emergent Universe supported by chiral cosmological fields in Einstein--Gauss--Bonnet gravity

TL;DR

This paper demonstrates that a chiral cosmological model within Einstein-Gauss-Bonnet gravity can support emergent universe scenarios across flat, open, and closed spatial geometries by deriving exact solutions with multiple scalar fields.

Contribution

It introduces a novel application of the chiral cosmological model to Einstein-Gauss-Bonnet gravity, providing exact solutions for the emergent universe scenario in various spatial curvatures.

Findings

Exact solutions for flat universe with two chiral fields.

Extension to open and closed universes with three chiral fields.

Both fields are phantom, with solutions depending on constant kinetic interaction.

Abstract

We propose the application of the chiral cosmological model (CCM) for the Einstein--Gauss--Bonnet (EGB) theory of gravitation with the aim of finding new models of the Emergent Universe (EmU) scenario. We analysed the EmU supported by two chiral cosmological fields for a spatially flat universe, while we have used three chiral fields when we investigated open and closed universes. To prove the validity of the EmU scenario we fixed the scale factor and found the exact solution by decomposition of EGB equations and solving the chiral field dynamics equation. To this end, we suggested the decomposition of the EGB equations in such a way that the first chiral field is responsible for the Einstein part of the model, while the second field, together with kinetic interaction term, is connected with the Gauss--Bonnet part of the theory. We proved that both fields are phantom ones under this decomposition, and that the model has a solution if the kinetic interaction between the fields equals a constant. We have presented the exact solution in terms of cosmic time. This was done for a spatially flat universe. In the case of open and closed universes we introduced the third chiral field (canonical for closed and phantom for open universe) which is responsible for the EGB and curvature parts. The solution of the third field equation is obtained in quadratures. Thus we have proved that the CCM is able to support EmU scenario in EGB gravity for spatially flat, open and closed universes.