Scalar perturbations in the late Universe: viability of the Chaplygin gas models

TL;DR

This paper investigates the late-time evolution of the universe using a modified generalized Chaplygin gas model, analyzing scalar perturbations and comparing with observational data to assess viability as dark energy and dark matter.

Contribution

It introduces a parameter selection for mGCG models compatible with the mechanical approach and observational data, evaluating their viability as dark energy and dark matter.

Findings

mGCG models are compatible with late-time universe observations

Selected parameter sets support mGCG as a unified dark sector

Analysis confirms the model's consistency with cosmic acceleration data

Abstract

We study the late-time evolution of the Universe where dark energy (DE) is parametrized by a modified generalized Chaplygin gas (mGCG) on top of cold dark matter (CDM). We also take into account the radiation content of the Universe. In this context, the late stage of the evolution of the universe refers to the epoch where CDM is already clustered into inhomogeneously distributed discrete structures (galaxies, groups and clusters of galaxies). Under these conditions, the mechanical approach is an adequate tool to study the Universe deep inside the cell of uniformity. To be more accurate, we study scalar perturbations of the Friedmann-Lema\^itre-Robertson-Walker metric due to inhomogeneities of CDM as well as fluctuations of radiation and mGCG, the later driving the late-time acceleration of the universe. Our analysis applies as well to the case where mGCG plays the role of DM and DE. We select the sets of parameters of the mGCG that are compatible with the mechanical approach. These sets define prospective mGCG models. By comparing the selected sets of models with some of the latest observational data results, we conclude that the mGCG is in tight agreement with those observations particularly for a mGCG playing the role of DE and DM.