On the concordance of cosmological data in the case of the generalized Chaplygin gas

The generalized Chaplygin gas cosmology provides a prime example for the class of unified dark matter models, which substitute the two dark components of the standard cosmological ΛCDM concordance model by a single dark component. The equation of state of the generalized Chaplygin gas is characterised by a parameter α such that the standard ΛCDM model is recovered in the case α=0 with respect to the background dynamics and the cosmic microwave background (CMB) statistics. This allows to investigate the concordance of different cosmological data sets with respect to α. We compare the supernova data of the Supernova Cosmology Project, the data of the baryon oscillation spectroscopic survey (BOSS) of the third Sloan digital sky survey (SDSS-III) and the CMB data of the Planck 2015 data release. The importance of the BOSS Lyman α forest BAO measurements is investigated. It is found that these data sets possess a common overlap of the confidence domains only for Chaplygin gas cosmologies very close to the ΛCDM model.