Shear viscosity and out of equilibrium dynamics
- Institut fuer Theoretische Physik, Goethe-Universitaet Frankfurt, Max-von-Laue Strasse 1, D-60438, Frankfurt am Main (Germany)
- 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, Vol. 79, Issue 4; Other Information: DOI: 10.1103/PhysRevC.79.044914; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
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