Viscous Cosmologies

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-Lamaître-Robertson-Walker metric. To this end we use a version of the energy-momentum tensor from the Müller-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.

49 pages, 18 figures

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Cited by in corpus (7)

• WIMP dark matter in bulk viscous non-standard cosmologies
• Lightening the Dark Matter from its Viscosity and Explanation of EDGES Anomaly
• FIMP Dark Matter in bulk viscous non-standard cosmologies
• Perfect fluid with shear viscosity and spacetime evolution
• Cosmology from Strong Interactions
• Homogeneous spacetime with shear viscosity
• Testing a nonlinear solution of the Israel-Stewart theory