Revisiting generalized Chaplygin gas as a unified dark matter and dark energy model

In this paper, we revisit the generalized Chaplygin gas (GCG) model as a unified dark matter and dark energy model. The energy density of GCG model is given as ρ _GCG/ ρ _GCG0=[ B _s +(1- B _s ) a ^{-3(1+ α)}]^{1/(1+ α)}, where α and B _s are two model parameters which will be constrained by type Ia supernova as standard candles, baryon acoustic oscillation as standard rulers and the seventh year full WMAP data points. In this paper, we will not separate GCG into dark matter and dark energy parts any more as adopted in the literature. By using the Markov Chain Monte Carlo method, we find the results α=0.00126_{-0.00126- 0.00126}^{+ 0.000970+ 0.00268} and B_s= 0.775_{-0.0161- 0.0338}^{+ 0.0161+ 0.0307}.