Phantom-like GCG and the constraints of its parameters via cosmological   dynamics
  We extend the equation of state of GCG (Generalized Chaplygin Gas) to $w<-1$ regime and show, from the point of view of dynamics, that the parameters of GCG should be in the range of $0<\alpha<1$. Also, dynamical analysis indicate that the phase $w_{g}=-1$ 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. 
Jian-gang Hao, Xin-zhou Li