Publikace ÚTF

Dark matter perturbations and viscosity: A causal approach

Acquaviva, G., John, A., Pénin, A.

The inclusion of dissipative effects in cosmic fluids modifies their clustering properties and could have
observable effects on the formation of large-scale structures. We analyze the evolution of density
perturbations of cold dark matter endowed with causal bulk viscosity. The perturbative analysis is carried
out in the Newtonian approximation and the bulk viscosity is described by the causal Israel-Stewart (IS)
theory. In contrast to the noncausal Eckart theory, we obtain a third-order evolution equation for the density
contrast that depends on three free parameters. For certain parameter values, the density contrast and
growth factor in IS mimic their behavior in ΛCDM when z ≥ 1. Interestingly, and contrary to intuition,
certain sets of parameters lead to an increase of the clustering.
journal:Phys. Rev. D

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