Condensation of a scalar field non-minimally coupled to gravity in a cosmological context

TL;DR

This paper introduces a new mechanism for scalar field condensation coupled to gravity via the Gauss-Bonnet term, leading to late-Universe acceleration and a de Sitter phase, with analysis of cosmological perturbations.

Contribution

It proposes a novel scalar field condensation mechanism in a cosmological setting, driven by coupling to the Gauss-Bonnet term, resulting in late-time acceleration.

Findings

Scalar field energy density decreases slower than background during radiation and dust eras.

Scalar field eventually dominates, leading to a de Sitter universe.

Cosmological perturbations of the model are analyzed and predictions explored.

Abstract

We present a new mechanism to condense a scalar field coupled to the Gauss-Bonnet term. We propose a scenario in which the condensed state will emerge from the background energy density in the late-Universe. During the radiation and dust-dominated eras, the energy density of the scalar field, $\rho_{\varphi}$, decreases at a slower rate than the background density. Eventually, $\rho_{\varphi}$ dominates over the energy density of dust and the scalar field could be condensed. In the condensed phase, we have the de Sitter phase for the universe with $\rho_{\varphi}=3H_0^2M_P^2$. Moreover, we study the cosmological perturbations of the model and explore predictions of the model.