Shear viscosity and out of equilibrium dynamics

Journal Article · Wed Apr 15 04:00:00 EDT 2009 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.79.044914· OSTI ID:21289878

El, Andrej; Zhe, Xu; Greiner, Carsten ^[1]; Muronga, Azwinndini ^[2]

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1. Institut fuer Theoretische Physik, Goethe-Universitaet Frankfurt, Max-von-Laue Strasse 1, D-60438, Frankfurt am Main (Germany)
2. Institute for Theoretical Physics and Astrophysics, Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa)

Using Grad's method, we calculate the entropy production and derive a formula for the second-order shear viscosity coefficient in a one-dimensionally expanding particle system, which can also be considered out of chemical equilibrium. For a one-dimensional expansion of gluon matter with Bjorken boost invariance, the shear tensor and the shear viscosity to entropy density ratio {eta}/s are numerically calculated by an iterative and self-consistent prescription within the second-order Israel-Stewart hydrodynamics and by a microscopic parton cascade transport theory. Compared with {eta}/s obtained using the Navier-Stokes approximation, the present result is about 20% larger at a QCD coupling {alpha}{sub s}{approx}0.3 (with {eta}/s{approx_equal}0.18) and is a factor of 2-3 larger at a small coupling {alpha}{sub s}{approx}0.01. We demonstrate an agreement between the viscous hydrodynamic calculations and the microscopic transport results on {eta}/s, except when employing a small {alpha}{sub s}. On the other hand, we demonstrate that for such small {alpha}{sub s}, the gluon system is far from kinetic and chemical equilibrium, which indicates the break down of second-order hydrodynamics because of the strong nonequilibrium evolution. In addition, for large {alpha}{sub s} (0.3-0.6), the Israel-Stewart hydrodynamics formally breaks down at large momentum p{sub T} > or approx. 3 GeV but is still a reasonably good approximation.

• OSTI ID: 21289878
• Journal Information: Physical Review. C, Nuclear Physics, Journal Name: Physical Review. C, Nuclear Physics Journal Issue: 4 Vol. 79; ISSN 0556-2813; ISSN PRVCAN
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
97 MATHEMATICS AND COMPUTING
APPROXIMATIONS
COMPUTERIZED SIMULATION
COUPLING
DENSITY
ENTROPY
EQUILIBRIUM
EXPANSION
GEV RANGE 01-10
GLUONS
HYDRODYNAMIC MODEL
ITERATIVE METHODS
NAVIER-STOKES EQUATIONS
ONE-DIMENSIONAL CALCULATIONS
QUANTUM CHROMODYNAMICS
SHEAR
TRANSPORT THEORY
VISCOSITY