The universe dominated by the extended Chaplygin gas

In this paper, we consider a universe dominated by the extended Chaplygin gas which was recently proposed as the last version of Chaplygin gas models. Here, we only consider the second-order term which recovers quadratic barotropic fluid equation of state. The density perturbations are analyzed in both relativistic and Newtonian regimes and show that the model is stable without any phase transition and critical point. We confirmed stability of the model using thermodynamics point of view.