http://arxiv.org/abs/1906.04162
In a spatially flat Friedmann-Lema\^{i}tre-Robertson-Walker universe, we investigate a unified cosmic fluid scenario endowed with bulk viscosity in which the coefficient of the bulk viscosity has a power law evolution. The power law in the bulk viscous coefficient is a general case in this study which naturally includes several choices as special cases. Considering such a general bulk viscous scenario, in the present work we have extracted the observational constraints using the latest cosmological datasets and examine their behaviour at the level of both background and perturbations. From the observational analyses, we find that a non-zero bulk viscous coefficient is always favored and some of the models in this series are able to weaken the current tension on $H_0$ for some dataset. At the level of perturbations, the models are very much sensitive to their free parameters. We find that the matter power spectra show an unusual blowing up for sufficient strength of the bulk viscous coefficient.
W. Yang, S. Pan, E. Valentino, et. al.
Tue, 11 Jun 19
57/60
Comments: 17 pages, 15 captioned figures, 5 tables; comments are welcome
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