Constraints on dissipative unified dark matter

Journal Article · Thu Sep 01 04:00:00 EDT 2011 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2011/09/016· OSTI ID:22277726

Velten, Hermano ^[1]

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1. Universidade Federal do Espírito Santo, Av. Fernando Ferrari, Goiabeiras, Vitória (Brazil)

Modern cosmology suggests that the Universe contains two dark components — dark matter and dark energy — both unkown in laboratory physics and both lacking direct evidence. Alternatively, a unified dark sector, described by a single fluid, has been proposed. Dissipation is a common phenomenon in nature and it thus seems natural to consider models dominated by a viscous dark fluid. We focus on the study of bulk viscosity, as isotropy and homogeneity at large scales implies the suppression of shear viscosity, heat flow and diffusion. The generic ansatz ξ∝ρ{sup ν} for the coefficient of bulk viscosity (ρ denotes the mass/energy density), which for ν = −1/2 mimics the ΛCDM background evolution, offers excellent fits to supernova and H(z) data. We show that viscous dark fluids suffer from large contributions to the integrated Sachs-Wolfe effect (generalising a previous study by Li and Barrow) and a suppression of structure growth at small-scales (as seen from a generalized Meszaros equation). Based on recent observations, we conclude that viscous dark fluid models (with ξ∝ρ{sup ν} and neglecting baryons) are strongly challenged.

• OSTI ID: 22277726
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 09 Vol. 2011; ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BARYONS
COSMOLOGICAL CONSTANT
COSMOLOGY
DIFFUSION
ENERGY DENSITY
EVOLUTION
FLUIDS
HEAT FLUX
ISOTROPY
MASS
NONLUMINOUS MATTER
SHEAR
UNIVERSE
VISCOSITY