History of cosmic evolution with modified Gauss-Bonnet-dilatonic coupled term

TL;DR

This paper develops a modified gravity model with Gauss-Bonnet-dilatonic coupling, unifying early inflation and late-time cosmic acceleration, and demonstrates its quantum consistency and phase-space formulation.

Contribution

It introduces a new scalar-tensor gravity theory with higher order curvature terms that unifies different cosmic epochs and addresses phase-space formulation issues.

Findings

Unifies early inflation with late-time acceleration.

Quantum version of the theory is well-behaved.

Provides a phase-space formulation for the modified theory.

Abstract

Gauss-Bonnet-dilatonic coupling in four dimension plays an important role to explain late time cosmic evolution. However, this term is an outcome of low energy string effective action and thus ought to be important in the early universe too. Unfortunately, phase-space formulation of such a theory does not exist in the literature due to branching. We therefore consider a modified theory of gravity, which contains a nonminimally coupled scalar-tensor sector in addition to higher order scalar curvature invariant term with Gauss-Bonnet-dilatonic coupling. Such an action unifies early inflation with late-time cosmic acceleration. Quantum version of the theory is also well-behaved.