Wednesday, July 25, 2012

1207.5582 (Suresh Kumar et al.)

Observational constraints on a cosmological model with variable equation
of state parameters for matter and dark energy
   [PDF]

Suresh Kumar, Lixin Xu
In this work we consider a spatially homogeneous and flat FRW space-time filled with non-interacting matter and dark energy components. The equation of state (EoS) parameters of the two sources are varied phenomenologically in terms of scale factor of the FRW space-time in such a way that the evolution of the Universe takes place from the early radiation-dominated phase to the present dark energy-dominated phase. We find parameters of the model in terms of redshift, which in principle are observationally testable and allow us to compare the derived model with observations. We constrain the model in two cases with the latest astronomical observations, and discuss the best fit model parameters in detail. First, we explore a special case of the model with WMAP+BAO+H0 observations by synchronizing the model with the $\Lambda$CDM model at the present epoch. An interesting point that emerges from this observational analysis is that the model is not only consistent with the $\Lambda$CDM predictions at the present epoch but also is indistinguishable from the $\Lambda$CDM model in revealing the future dynamics of the Universe. In the second case, we find observational constraints on general class of the model from Supernova+BAO observations. The derived model, in the general case, predicts age of the Universe, Hubble constant, density parameters and equation of state parameter of dark energy consistent with the ones obtained from seven year WMAP observations. The model advocates cosmological constant as a candidate of dark energy (DE), which is consistent with the WMAP observations. Finally, we conclude that the derived model offers a unified description of the evolution of Universe from the early radiation-dominated phase to the present DE-dominated phase in accord with the current astronomical observations. The model is physically viable and is applicable to the real Universe.
View original: http://arxiv.org/abs/1207.5582

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