III, JF; Demir, NS; Srivastava, DK; Bass, SA, *Shear viscosity in a perturbative quark-gluon plasma*,
Journal of Physics G: Nuclear and Particle Physics, vol. 38 no. 1
(Spring, 2011),
pp. 015004 [doi] .
**Abstract:**

*Among the key features of hot and dense QCD matter produced in ultra-relativistic heavy-ion collisions at RHIC is its very low shear viscosity, indicative of the properties of a near-ideal fluid, and a large opacity demonstrated by jet energy loss measurements. In this work, we utilize a microscopic transport model based on the Boltzmann equation with quark and gluon degrees of freedom and cross sections calculated from perturbative quantum chromodynamics to simulate an ideal quark-gluon plasma in full thermal and chemical equilibrium. We then use the Kubo formalism to calculate the shear viscosity to entropy-density ratio of the medium as a function of temperature and system composition. One of our key results is that the shear viscosity over entropy-density ratio η/s becomes invariant to the chemical composition of the system when plotted as a function of energy-density instead of temperature. © 2011 IOP Publishing Ltd.*