Suppression of the shear viscosity near the critical temperature in hot QCD Original Research Article

We consider QCD near but above critical temperature Tc. The pressure, susceptibilities and the renormalized Polyakov loop — which is an order parameter for the deconfining phase transition — dramatically change up to temperatures a few times Tc. We refer to this region as a “semi”-QGP, where partial confinement plays important role. We show that the shear viscosity η is suppressed by two powers of the Polyakov loop. This suggests that η/T3 decreases markedly as QCD cools down to temperatures near Tc. We also show a ratio of the viscosity to the entropy becomes small near Tc [Y. Hidaka and R.D. Pisarski, Phase," arXiv:0803.0453 [Phys. Rev. D (to be published)]].