Viscous dark fluid Universe: a unified model of the dark sector?

Details Viscous dark fluid Universe: a unified model of the dark sector? Viscous dark fluid Universe: a unified model of the dark sector?

2011-11-20

arxiv.org/abs/1111.4694v1

International Journal of Modern Physics: Conference Series, Vol. 3 (2011) 312-323

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

12 pages, 3 figures, contributed paper to 8th Friedmann Seminar, 30 May to 3 June 2011, Rio de Janeiro, Brazil

Scientific paper

10.1142/S2010194511001413

The Universe is modeled as consisting of pressureless baryonic matter and a bulk viscous fluid which is supposed to represent a unified description of the dark sector. In the homogeneous and isotropic background the \textit{total} energy density of this mixture behaves as a generalized Chaplygin gas. The perturbations of this energy density are intrinsically nonadiabatic and source relative entropy perturbations. The resulting baryonic matter power spectrum is shown to be compatible with the 2dFGRS and SDSS (DR7) data. A joint statistical analysis, using also Hubble-function and supernovae Ia data, shows that, different from other studies, there exists a maximum in the probability distribution for a negative present value of the deceleration parameter. Moreover, the unified model presented here favors a matter content that is of the order of the baryonic matter abundance suggested by big-bang nucleosynthesis. A problem of simple bulk viscous models, however, is the behavior of the gravitational potential and the reproduction of the CMB power spectrum.

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