Shear viscosity and entropy of quark matter

We consider the shear viscosity of a system of quarks and its ratio to the entropy density above the critical temperature for deconfinement. Expressions for both quantities are derived in the quasi-particle approximation and calculations are carried out for different modeling of the quark self-energy, also allowing for a temperature dependence of the effective mass and width. Beyond the temperature dependence, the behaviour of the viscosity and the entropy density is discussed in terms of the strength of the coupling and of the main characteristics of the quark self-energy. A comparison with existing approaches is also discussed