De Sitter ground state of scalar-tensor gravity and its fluctuation with dust

TL;DR

This paper presents an exact de Sitter solution in scalar-tensor gravity, demonstrating how a non-minimal scalar field can induce dynamic dark energy behaviors, including crossing the phantom divide, in dust-filled FRW universes.

Contribution

It introduces a novel exact de Sitter solution in scalar-tensor gravity with a rolling scalar field and explores its implications for dark energy dynamics in cosmology.

Findings

Scalar-tensor gravity admits an exact de Sitter solution with a non-constant potential.

The effective dark energy can behave as quintessence or phantom energy.

The scalar field dynamics allow crossing the phantom divide in dust-filled universes.

Abstract

An exact de Sitter solution of scalar-tensor gravity is found, in which the non-minimal coupling scalar is rolling along a non-constant potential. Based on this solution, a dust-filled FRW universe is explored in frame of scalar-tensor gravity. The effective dark energy induced by the sole non-minimal scalar can be quintessence-like, phantom-like, and more significantly, can cross the phantom divide. The rich and varied properties of scalar-tensor gravity even with only one scalar is shown in this article.