Hubble Parameter in QCD Universe for finite Bulk Viscosity

Abstract

We consider the influence of the perturbative bulk viscosity on the evolution of the Hubble parameter in the QCD era of the early Universe. For the geometry of the Universe we assume the homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker metric, while the background matter is assumed to be characterized by barotropic equations of state, obtained from recent lattice QCD simulations, and heavy--ion collisions, respectively. Taking into account a perturbative form for the bulk viscosity coefficient, we obtain the evolution of the Hubble parameter, and we compare it with its evolution for an ideal (non-viscous) cosmological matter. A numerical solution for the viscous QCD plasma in the framework of the causal Israel-Stewart thermodynamics is also obtained. Both the perturbative approach and the numerical solution qualitatively agree in reproducing the viscous corrections to the Hubble parameter, which in the viscous case turns out to be slightly different as compared to the non--viscous case. Our results are strictly limited within a very narrow temperature- or time-interval in the QCD era, where the quark-gluon plasma is likely dominant.

9 pages (revtex4 style), 5 figures with 8 eps graphs

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Cited by in corpus (14)

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• Quark-Hadron Phase Transitions in Viscous Early Universe
• Effects of quantum gravity on the inflationary parameters and thermodynamics of the early universe
• On the bulk viscosity of anisotropically expanding hot QCD plasma
• Lorentz Invariance Violation and Generalized Uncertainty Principle
• Bulk Viscous Matter-dominated Universes: Asymptotic Properties
• Matter-Antimatter Asymmetry in the Large Hadron Collider
• An estimate of the bulk viscosity of the hadronic medium
• Thermodynamics of viscous Matter and Radiation in the Early Universe
• Bulk viscosity in strong and electroweak matter
• QCD phase transition with a power law chameleon scalar field in the bulk
• Quark-Hadron Phase Transition in DGP Brane Gravity with Bulk Scalar Field