Observational constraint on generalized Chaplygin gas model
  We investigate observational constraints on the generalized Chaplygin gas
(GCG) model as the unification of dark matter and dark energy from the latest
observational data: the Union SNe Ia data, the observational Hubble data, the
SDSS baryon acoustic peak and the five-year WMAP shift parameter. It is
obtained that the best fit values of the GCG model parameters with their
confidence level are $A_{s}=0.73^{+0.06}_{-0.06}$ ($1\sigma$)
$^{+0.09}_{-0.09}$ $(2\sigma)$, $\alpha=-0.09^{+0.15}_{-0.12}$ ($1\sigma$)
$^{+0.26}_{-0.19}$ $(2\sigma)$. Furthermore in this model, we can see that the
evolution of equation of state (EOS) for dark energy is similar to quiessence,
and its current best-fit value is $w_{0de}=-0.96$ with the $1\sigma$ confidence
level $-0.91\geq w_{0de}\geq-1.00$.
