Viscous generalized Chaplygin gas

Abstract

Viscous GCG(generalized Chaplygin gas) cosmology is discussed, assuming that there is bulk viscosity in the barotropic fluid and GCG. The dynamical analysis indicates that the phase $w_g=-1+\sqrt{3}\gamma\kappa\tau_{g}/(\gamma-\sqrt{3}\kappa\tau_{\gamma})$ is a dynamical attractor and the equation of state of GCG approaches it from either $w_g>-1$ or $w_g<-1$ depending on the choice of its initial cosmic density parameter and the ratio of pressure to critical energy density. Obviously, the equation of state $w_g$ can cross the boundary $w_g=-1$. Also, from the point of view of dynamics, the parameters of viscous GCG should be in the range of $\gamma>\sqrt{3}\kappa\tau_{\gamma}/(1-\sqrt{3}\kappa\tau_{g})$ and $0<\alpha<1+\sqrt{3} \kappa\gamma\tau_{g}/(\gamma-\sqrt{3}\kappa\tau_{\gamma}-\sqrt{3}\kappa\gamma\t au_{g})$.