A new phase of scalar field with a kinetic term non-minimally coupled to gravity

TL;DR

This paper introduces a novel phase of a non-minimally coupled scalar field in cosmology, characterized by unique dynamics and an accelerating universe, distinct from inflation and reheating, with implications for scalar field interactions.

Contribution

The study identifies and analytically describes a new scalar field phase with non-minimal coupling, expanding understanding of scalar field dynamics in cosmological models.

Findings

Existence of a new scalar field phase with accelerating expansion

Analytic solutions for scalar field and Hubble parameter in the new phase

Absence of parametric resonance in the scalar field interactions

Abstract

We consider the dynamics of a scalar field non-minimally coupled to gravity in the context of cosmology. It is demonstrated that there exists a new phase for the scalar field, in addition to the inflationary and dust-like (reheating period) phases. Analytic expressions for the scalar field and the Hubble parameter, which describe the new phase are given. The Hubble parameter indicates an accelerating expanding Universe. We explicitly show that the scalar field oscillates with time- dependent frequency. Moreover, an interaction between the scalar field in the new phase and other fields is discussed. It turns out that the parametric resonance is absent, which is another crucial difference between the dynamics of the scalar field in the new phase and dust-like phase.