Cosmic bulk viscosity through backreaction

Abstract

We consider an effective viscous pressure as the result of a backreaction of inhomogeneities within Buchert's formalism. The use of an effective metric with a time-dependent curvature radius allows us to calculate the luminosity distance of the backreaction model. This quantity is different from its counterpart for a "conventional" spatially flat bulk viscous fluid universe. Both expressions are tested against the SNIa data of the Union2.1 sample with only marginally different results for the distance-redshift relation and in accordance with the $\Lambda$CDM model. Future observations are expected to be able to discriminate among these models on the basis of indirect measurements of the curvature evolution.

18 pages, 6 figures, comments and references added, accepted for publication in GRG

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• On average properties of inhomogeneous fluids in general relativity III: general fluid cosmologies
• Dark Matter from Backreaction? Collapse models on galaxy cluster scales
• Replacing dark energy by silent virialisation
• Gauss-Bonnet-Chern approach to the averaged Universe
• Future evolution in a backreaction model and the analogous scalar field cosmology
• The background Friedmannian Hubble constant in relativistic inhomogeneous cosmology and the age of the Universe
• Lagrangian theory of structure formation in relativistic cosmology. V. Irrotational fluids
• Averaged Lemaître-Tolman-Bondi dynamics
• Does spatial flatness forbid the turnaround epoch of collapsing structures?
• Does relativistic cosmology software handle emergent volume evolution?