Chameleon dark energy models with characteristic signatures

TL;DR

This paper explores chameleon dark energy models that can produce observable cosmological signatures while satisfying local gravity constraints, proposing a new potential inspired by f(R) gravity that affects structure growth.

Contribution

The authors introduce a novel chameleon potential based on f(R) gravity, enabling observable effects in both background evolution and structure growth within local gravity bounds.

Findings

Growth index gamma_0 can be less than 0.2

Significant dispersion in gamma on low redshifts

Potential to distinguish from Lambda-CDM in future observations

Abstract

In chameleon dark energy models, local gravity constraints tend to rule out parameters in which observable cosmological signatures can be found. We study viable chameleon potentials consistent with a number of recent observational and experimental bounds. A novel chameleon field potential, motivated by f(R) gravity, is constructed where observable cosmological signatures are present both at the background evolution and in the growth-rate of the perturbations. We study the evolution of matter density perturbations on low redshifts for this potential and show that the growth index today gamma_0 can have significant dispersion on scales relevant for large scale structures. The values of gamma_0 can be even smaller than 0.2 with large variations of gamma on very low redshifts for the model parameters constrained by local gravity tests. This gives a possibility to clearly distinguish these chameleon models from the Lambda-Cold-Dark-Matter model in future high-precision observations.