A model of the late universe with viscous Zel’ldovich fluid and decaying vacuum
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Many have speculated about the presence of a stiff fluid in very early stage of the universe. Such a stiff fluid was first introduced by Zel’dovich. Recently the late acceleration of the universe was studied by taking bulk viscous stiff fluid as the dominant cosmic component, but the age predicted by such a model is less than the observed value. We consider a flat universe with viscous stiff fluid and decaying vacuum energy as the cosmic components and found that the model predicts a reasonable background evolution of the universe with de Sitter epoch as end phase of expansion. More over, the model also predicts a reasonable value for the age of the present universe. We also performed a dynamical system analysis of the model and found that the end de Sitter phase predicted by the model is stable.
KeywordsCosmology Accelerating universe Stiff fluid Decaying vacuum
One of the authors (KRN) thanks CUSAT Kochi, India for financial support in the form of a research fellowship. We also wish to thank IUCAA, Pune, India for the local hospitality during our visits, where part of the work had been carried out.
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