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Large scale structure from viscous dark matter | Diego Blas
; Stefan Floerchinger
; Mathias Garny
; Nikolaos Tetradis
; Urs Achim Wiedemann
; | Date: |
23 Jul 2015 | Abstract: | Cosmological perturbations of sufficiently long wavelength admit a fluid
dynamic description. We consider modes with wavevectors below a scale $k_m$ for
which the dynamics is only mildly non-linear. The leading effect of modes above
that scale can be accounted for by effective non-equilibrium viscosity and
pressure terms. For mildly non-linear scales, these mainly arise from momentum
transport within the ideal and cold but inhomogeneous fluid, while momentum
transport due to more microscopic degrees of freedom is suppressed. As a
consequence, concrete expressions with no free parameters, except the matching
scale $k_m$, can be derived from matching evolution equations to standard
cosmological perturbation theory. Two-loop calculations of the matter power
spectrum in the viscous theory lead to excellent agreement with $N$-body
simulations up to scales $k=0.2 , h/$Mpc. The convergence properties in the
ultraviolet are better than for standard perturbation theory and the results
are robust with respect to variations of the matching scale. | Source: | arXiv, 1507.6665 | Services: | Forum | Review | PDF | Favorites |
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