9 research outputs found
Newtonian Approach to the Matter Power Spectrum of the Generalized Chaplygin Gas
We model the cosmic medium as the mixture of a generalized Chaplygin gas and
a pressureless matter component. Within a neo-Newtonian approach we compute the
matter power spectrum. The 2dFGRS data are used to discriminate between unified
models of the dark sector and different models, for which there is separate
dark matter, in addition to that accounted for by the generalized Chaplygin
gas. Leaving the corresponding density parameters free, we find that the
unified models are strongly disfavored. On the other hand, using unified model
priors, the observational data are also well described, in particular for small
and large values of the generalized Chaplygin gas parameter .Comment: Latex file, 5 pages, 11 figures in eps format. For the proceedings of
the conference Dark Energy and Dark Matter, 7-11 july 2008, Lyon, Franc
Ruling out the Modified Chaplygin Gas Cosmologies
The Modified Chaplygin Gas (MCG) model belongs to the class of a unified
models of dark energy (DE) and dark matter (DM). It is characterized by an
equation of state (EoS) , where the case
corresponds to the Generalized Chaplygin Gas (GCG) model. Using a perturbative
analysis and power spectrum observational data we show that the MCG model is
not a sucessful candidate for the cosmic medium unless . In this case, it
reduces to the usual GCG model.Comment: Latex file, 7 pages, 6 figures in eps forma
Constraints on the Generalized Chaplygin Gas Model from Gamma-Ray Bursts
We study the Generalized Chaplygin gas model (GCGM) using Gamma-ray bursts as
cosmological probes. In order to avoid the so-called circularity problem we use
cosmology-independent data set and Bayesian statistics to impose constraints on
the model parameters. We observe that a negative value for the parameter
is favoured if we adopt a flat Universe and the estimated value of the
parameter is lower than that found in literature.Comment: 10 pages, 29 figures, accepted for publication in Physics Letters