Chameleon Mechanism in Scalar Nonmetricity Cosmology

TL;DR

This paper explores scalar nonmetricity cosmology with a Chameleon mechanism, analyzing how different connection choices influence scalar-matter interactions and phase-space dynamics in a generalized Brans-Dicke framework.

Contribution

It introduces a generalized scalar nonmetricity theory with a Chameleon mechanism, highlighting the impact of connection choices on scalar-matter interactions and cosmological solutions.

Findings

Connection choice affects scalar-matter interaction dynamics.

No asymptotic solutions with nontrivial interaction for a specific connection.

Matter interacts with connection degrees of freedom, not directly with the scalar field.

Abstract

We investigate the dynamics and the phase-space evolution for the scalar nonmetricity cosmology with a Chameleon mechanism. In particular, we consider a spatially flat Friedmann--Lema\^{\i}tre--Robertson--Walker geometry and within the framework of scalar nonmetricity theory, we consider a generalization of the Brans-Dicke theory in nonmetricity gravity. Introducing a pressureless gas as the matter source, we also incorporate a coupling function responsible for the interaction. Our findings reveal that the choice of connection in nonmetricity gravity significantly impacts the interaction between the scalar field and the matter source. For one particular connection, we discover the absence of asymptotic solutions with a nontrivial interacting component. More precisely, in this scenario, the matter source does not directly interact with the scalar field; however, there is an interaction with the dynamical degrees of freedom provided by the connection.