منابع مشابه
‘Understanding’ cosmological bulk viscosity
A universe consisting of two interacting perfect fluids with the same 4-velocity is considered. A heuristic mean free time argument is used to show that the system as a whole cannot be perfect as well but neccessarily implies a nonvanishing bulk viscosity. A new formula for the latter is derived and compared with corresponding results of radiative hydrodynamics.
متن کاملEffects of Bulk Viscosity on Cosmological Evolution
The effect of bulk viscisity on the evolution of the homogeneous and isotropic cosmological models is considered. Solutions are found, with a barotropic equation of state, and a viscosity coefficient that is proportional to a power of the energy density of the universe. For flat space, power law expansions, related to extended inflation are found as well as exponential solutions, related to old...
متن کاملCosmological solutions with nonlinear bulk viscosity
A recently proposed nonlinear transport equation is used to model bulk viscous cosmologies that may be far from equilibrium, as happens during viscous fluid inflation or during reheating. The asymptotic stability of the de Sitter and Friedmann solutions is investigated. The former is stable for bulk viscosity index q < 1 and the latter for q > 1. New solutions are obtained in the weakly nonline...
متن کاملAccelerating cosmological expansion from shear and bulk viscosity.
The dissipation of energy from local velocity perturbations in the cosmological fluid affects the time evolution of spatially averaged fluid dynamic fields and the cosmological solution of Einstein's field equations. We show how this backreaction effect depends on shear and bulk viscosity and other material properties of the dark sector, as well as the spectrum of perturbations. If sufficiently...
متن کاملGeneral Bulk-Viscous Solutions and Estimates of Bulk Viscosity in the Cosmic Fluid
We derive a general formalism for bulk viscous solutions of the energy-conservation equation for ρ(a, ζ), both for a single-component and a multicomponent fluid in the Friedmann universe. For our purposes, these general solutions become valuable in estimating the order of magnitude of the phenomenological viscosity in the cosmic fluid at present. H(z) observations are found to put an upper limi...
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ژورنال
عنوان ژورنال: Monthly Notices of the Royal Astronomical Society
سال: 2016
ISSN: 0035-8711,1365-2966
DOI: 10.1093/mnras/stw102