Abstract
In this paper we consider a flat FLRW universe with bulk viscous Zel’dovich fluid as the cosmic component. Considering the bulk viscosity as characterized by a constant bulk viscous coefficient, we analyze the evolution of the Hubble parameter. Type Ia Supernovae data is used for constraining the model and for extracting the constant bulk viscous parameter and present the Hubble parameter. We also present the analysis of the scale factor, equation of state, and deceleration parameter. The model predicts the later time acceleration and is also compatible with the age of the universe as given by the oldest globular clusters. Study of the phase-space behavior of the model shows that a universe dominated by bulk viscous Zel’dovich fluid is stable. But the inclusion of a radiation component in addition to the Zel’dovich fluid makes the model unstable. Hence, even though the bulk viscous Zel’dovich fluid dominated universe is a feasible one, the model as such fails to predict a prior radiation dominated phase.
Highlights
Observational data on Type-Ia supernovae [1,2,3] and the CMB [4,5] has confirmed with sufficient accuracy that nearly 70 percent of energy of the universe is in an exotic form called dark energy, which is responsible for the current acceleration of the universe
In this paper we have considered a flat universe consisting of a bulk viscous Zel’dovich fluid
We have evaluated the evolution of the Hubble parameter
Summary
Observational data on Type-Ia supernovae [1,2,3] and the CMB [4,5] has confirmed with sufficient accuracy that nearly 70 percent of energy of the universe is in an exotic form called dark energy, which is responsible for the current acceleration of the universe. [32], it was shown that the non-viscous Zel’dovich fluid density will evolve as ρz ∼ a−6, in a flat universe with expansion scale factor a In such a case the Zel’dovich fluid has a notable effect only on the early evolution of universe compared to ordinary dark matter, whose density evolves as a−3. The authors of [32] considered this model and proved that a bulk viscous Zel’dovich fluid does produce late acceleration of the universe They did not try to constrain the model with cosmological observational data to arrive at a realistic picture. In the present work we analyze the evolution of a flat universe with a bulk viscous Zel’dovich fluid and compare the predictions of the model with the latest cosmological data on type Ia supernovae.
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