Abstract
Recent observational predictions suggest that our Universe is passing through an accelerating phase in the recent past. This acceleration may be realized with the negatively pressured dark energy. Generalized Chaplygin gas may be suitable to describe the evolution of the Universe as a candidate of unified dark matter energy (UDME) model. Its EoS parameters are constrained using (i) dimensionless age parameter (H 0 t 0) and (ii) the observed Hubble (H(z)−z) data (OHD) + baryon acoustic oscillation (BAO) data + cosmic microwave background (CMB) shift data + supernovae (Union2.1) data. Dimensionless age parameter puts loose bounds on the EoS parameters. Best-fit values of the EoS parameters H 0, A s and α (A s and α are defined in the energy density for generalized Chaplygin gas (GCG) and in EoS) are then determined from OHD + BAO + CMB + Union2.1 data and contours are drawn to obtain their allowed range of values. The present age of the Universe (t 0) and the present Hubble parameter (H 0) have been estimated with 1σ confidence level. Best-fit values of deceleration parameter (q), squared sound speed ( $c_{\mathrm {s}}^{2}$ ) and EoS parameter (ω) of this model are then determined. It is seen that GCG satisfactorily accommodates an accelerating phase and structure formation phase.
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