Observational Constraints on the Unified Dark-Energy--Dark-Matter Model

We investigate the constraints on a generalized Chaplygin gas (GCG) model using the gold sample type-Ia supernovae (Sne Ia) data, the new Supernova Legacy Survey (SNLS) Sne Ia data and the size of baryonic acoustic oscillation peak found in Sloan Digital Sky Survey (SDSS). In a spatially flat universe case we obtain, at a 95.4% confidence level, A_s=0.76_-0.07^+0.07 and α=0.028_-0.238^+0.322. Our results are consistent with the ΛCDM model (α=0), but rule out the standard Chaplygin gas model (α=1).