Matter power spectrum for the generalized Chaplygin gas model: The relativistic case

TL;DR

This paper investigates the matter power spectrum in the generalized Chaplygin gas model within a relativistic framework, using observational data to constrain parameters and exploring the viability of unified dark energy and dark matter models.

Contribution

It provides a relativistic analysis of the GCG model's matter power spectrum and assesses the model's validity with observational constraints and a two-component dark sector analysis.

Findings

Small and large values of alpha are preferred by data.

The universe is likely dominated by separate dark matter with negligible GCG.

The analysis confirms previous Newtonian results.

Abstract

The generalized Chaplygin gas (GCG) model is the prototype of a unified model of dark energy (DE) and dark matter (DM). It is characterized by equation-of-state (EoS) parameters $A$ and $\alpha$. We use a statistical analysis of the 2dFGRS data to constrain these parameters. In particular, we find that very small (close to zero) and very large values ($\alpha\gg 1$) of the equation-of-state parameter $\alpha$ are preferred. To test the validity of this type of unification of the dark sector we admit the existence of a separate DM component in addition to the Chaplygin gas and calculate the probability distribution for the fractional contributions of both components to the total energy density. This analysis favors a model for which the Universe is nearly entirely made up of the separate DM component with an almost negligible Chaplygin gas part. This confirms the results of a previous Newtonian analysis.