Viscous generalized Chaplygin gas
  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 $0<\alpha<1+\sqrt{3} \kappa\gamma\tau_{g}/(\gamma-\sqrt{3}\kappa\tau_{\gamma}-\sqrt{3}\kappa\gamma\t au_{g})$. 
Xiang-hua Zhai, You-dong Xu, Xin-zhou Li