Cosmic Acceleration and Geodesic Deviation in Chameleon Scalar Field Model

TL;DR

This paper explores how a chameleon scalar field model can explain the universe's late-time acceleration and examines geodesic deviation to connect theoretical predictions with observable quantities.

Contribution

It analyzes the late-time acceleration in a chameleon scalar field model with constraints on parameters and derives geodesic deviation equations for observational comparison.

Findings

Strong matter-scalar coupling needed for acceleration

Derived geodesic deviation equations in chameleon model

Calculated observer area-distance for model validation

Abstract

While considering the chameleon scalar field model with the spatially flat FLRW background, we investigate the late-time acceleration phase of the universe, wherein we apply the typical potential usually used in this model. Through setting some constraints on the free parameters of the model, we indicate that the non-minimal coupling between the matter and the scalar field in such a model should be strongly coupled in order to have an accelerated expansion of the universe at the late-time. We also investigate the relative acceleration of the parallel geodesics by obtaining the geodesic deviation equation in the context of chameleon model. Then, through the null deviation vector fields, we obtain the observer area-distance as a measurable quantity to compare the model with other relevant models.