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 $0<\alpha<1+\sqrt{ 3} \kappa\gamma\tau_{ g}/(\gamma-\sqrt{ 3}\kappa\tau_{ \gamma}-\sqrt{ 3}\kappa\gamma\t au_{ g})$.
Categories: astro-ph