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arXiv · 1901.09787

Viscous Cosmologies

Sergio Bravo Medina·Marek Nowakowski·Davide Batic
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Abstract

We probe into universes filled with Quark Gluon Plasma with non-zero viscosities. In particular, we study the evolution of a universe with non-zero shear viscosity motivated by the theoretical result of a non-vanishing shear viscosity in the Quark Gluon Plasma due to quantum-mechanical effects. We first review the consequences of a non-zero bulk viscosity and show explicitly the non-singular nature of the bulk-viscosity-universe by calculating the cosmological scale factor $R(t)$ which goes to zero only asymptotically. We further extend the model of bulk viscosity to include a Cosmological Constant. We contrast the previous results with the cosmology of universes with non-zero shear viscosity. We first clarify under which conditions shear viscosity terms are compatible with the Friedmann-Lama\^itre-Robertson-Walker metric. To this end we use a version of the energy-momentum tensor from the M\"uller-Isreal-Stewart theory which leads to causal Navier-Stoke equations. We then derive the corresponding Friedmann equations and show under which conditions the universe emerges non-singular.

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Sergio Bravo Medina, Marek Nowakowski, Davide Batic. 2019-01-28. Viscous Cosmologies. https://doi.org/10.1088/1361-6382%2Fab45bb

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