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arXiv · 0801.3368

On the Role of Viscosity in Early Cosmology

Nakia Carlevaro·Giovanni Montani
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Abstract

We present a discussion of the effects induced by bulk viscosity on the very early Universe stability. The viscosity coefficient is assumed to be related to the energy density $ρ$ via a power-law of the form $ζ=ζ_0 ρ^s$ (where $ζ_0, s=const.$) and the behavior of the density contrast in analyzed. In particular, we study both Einstein and hydrodynamic equations up to first and second order in time in the so-called quasi-isotropic collapsing picture near the cosmological singularity. As a result, we get a power-law solution existing only in correspondence to a restricted domain of $ζ_0$. The particular case of pure isotropic FRW dynamics is then analyzed and we show how the asymptotic approach to the initial singularity admits an unstable collapsing picture.

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Nakia Carlevaro, Giovanni Montani. 2008-04-24. On the Role of Viscosity in Early Cosmology. https://doi.org/10.1142/s0217751x08040160

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