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

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 betweenCDMand 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 (Blas et al., 2011) 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 vertical bar alpha vertical bar less than or similar to 0.05, i.e., to values very close to the CDM limit alpha = 0. This excludes, in particular, models in which DE decays linearly with the Hubble rate. (C) 2017 Elsevier B.V. All rights reserved.