Does a generalized Chaplygin gas correctly describe the cosmological dark sector?

TL;DR

This paper investigates whether a generalized Chaplygin gas can accurately describe the universe's dark sector, finding it only fits well when its parameters are very close to the standard cosmological model.

Contribution

It reanalyzes the cosmological dynamics of a generalized Chaplygin gas split into dark matter and dark energy, constraining its parameters using CMB and matter power spectra data.

Findings

gCg parameter α is constrained to |α| ≲ 0.05

Models with linear DE decay are excluded

gCg closely mimics ΛCDM when α ≈ 0

Abstract

Yes, but only for a parameter value that makes it almost coincide with the standard model. We reconsider the cosmological dynamics of a generalized Chaplygin gas (gCg) which is split into a cold dark matter (CDM) part and a dark energy (DE) component with constant equation of state. This model, which implies a specific interaction between CDM and DE, has a $\Lambda$CDM limit and provides the basis for studying deviations from the latter. Including matter and radiation, we use the (modified) CLASS code \cite{class} to construct the CMB and matter power spectra in order to search for a gCg-based concordance model that is in agreement with the SNIa data from the JLA sample and with recent Planck data. The results reveal that the gCg parameter $\alpha$ is restricted to $|\alpha|\lesssim 0.05$, i.e., to values very close to the $\Lambda$CDM limit $\alpha =0$. This excludes, in particular, models in which DE decays linearly with the Hubble rate.