Inflationary generalized Chaplygin gas and dark energy in the light of the Planck and BICEP2 experiments

Abstract

In this work, we study an inflationary scenario in the presence of Generalized Chaplygin Gas (GCG). We show that in Einstein gravity, GCG is not a suitable candidate for inflation; but in a five dimensional brane world scenario, it can work as a viable inflationary model. We calculate the relevant quantities such as $n_{s}$, $r$ and $A_{s}$ related to the primordial scalar and tensor fluctuations, and using their recent bounds from Planck and BICEP2, we constrain the model parameters as well as the five-dimensional Planck mass. But as a slow-roll inflationary model with a power-law type scalar primordial power spectrum, GCG as an inflationary model can not resolve the tension between results from BICEP2 and Planck with a concordance $\Lambda$CDM Universe. We show that going beyond the concordance $\Lambda$CDM model and incorporating more general dark energy behaviour, this tension may be eased. We also obtain the constraints on the $n_{s}$ and $r$ and the GCG model parameters using Planck+WP+BICEP2 data considering the CPL dark energy behaviour.Comment: 12 pages, Latex style, 7 eps figures, 1 tabl