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

References in corpus (4)

• Relativistic viscous hydrodynamics, conformal invariance, and holography
• The QCD Equation of State with almost Physical Quark Masses
• Bulk viscosity of QCD matter near the critical temperature
• Experimental Tests of Asymptotic Freedom

Cited by in corpus (14)

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• 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
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• 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