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HK: Fachverband Hadronen und Kerne
HK 12: Heavy Ion Collisions and QCD phases
HK 12.4: Talk
Monday, March 16, 2009, 17:45–18:00, H-ZO 10
Shear viscosity and out of equilibrium dissipative hydrodynamics — •Andrej El, Zhe Xu, and Carsten Greiner — Goethe Universität Frankfurt am Main
We compare the solution of Israel-Stewart equations in (0+1) dimensions for a system with ongoing chemical equilibration to the results of calculations by microscopic partonic cascade BAMPS with pQCD 2↔ 2 and 2↔ 3 processes implemented. The shear viscosity coefficient needed to solve IS equations is calculated by an expression, which is derived from kinetic theory using Grad’s method. We demonstrate an agreement between the viscous hydrodynamic calculations and the microscopic transport results on η/s, except when employing a small αs. At αs=0.3 we obtain η/s≈ 0.18. On the other hand we demonstrate that for such small αs the gluon system is far from kinetic and chemical equilibrium, which indicates the break down of hydrodynamics. The comparison of dissipative hydrodynamic and BAMPS calculations shows the importance of chemical equilibration: without an ongoing chemical equilibration the system evolves faster to a state where hydrodynamics becomes invalid.