The evolution of generalized Chaplygin gas

We consider the generalized Chaplygin gas (GCG) proposal for the unification of dark matter and dark energy with p = p(de) and rho = rho(dm) + rho(de). The unified equation of state for GCG has been obtained: chi(z) = -omega(0de)Omega(0de)/omega(0de)Omega(0de)-(1+omega(0de))(1+z)(3(1+alpha)). On the basis of the function chi(z), some cosmological quantities such as the fractional contributions of different components of the universe Omega(i) (i respectively denotes baryons, dark matter and dark energy) to the critical density, the equation of state for dark energy omega(de), the deceleration parameter q are all obtained, which are consistent with observations. In addition, the transition from deceleration to acceleration is described in our model. We find that the behavior of GCG will be like Lambda CDM in the future. So, it has been ruled out in our model that our universe will end up with Big Rip in the future.