Dynamical interplay between coupled scalar dark sectors and gravity

TL;DR

This paper introduces a new cosmological model where coupled scalar fields interact with gravity within scalar-tensor theories, analyzing their stability and compatibility with the universe's history, and exploring implications for the cosmic coincidence problem.

Contribution

It extends axion-dilaton systems by incorporating non-minimal couplings with gravity, providing new insights into scalar field interactions and their cosmological implications.

Findings

Model is compatible with the universe's recent history

Viable parameter constraints identified for the model

Distinct phase-space features may alleviate the cosmic coincidence problem

Abstract

We explore a novel cosmological model based on coupled fields in the framework of scalar tensor theories, considering the specific interplay between gravity and scalar fields. The model further extends a recent axion-dilaton system by introducing viable couplings with the space--time geometry encoded into the scalar curvature. After briefly introducing the action and the corresponding field equations, we employ linear stability theory to investigate the physical properties. The analysis showed the compatibility of the current theoretical model with the recent history of the Universe, obtaining viable constraints for the model's parameters in some specific cases. In the present setup, the axion--dilaton system is non--minimally coupled with gravity in an independent manner, leading to distinct physical features in the phase-space structure, possible alleviating the cosmic coincidence problem.