Suppression of the shear viscosity near the critical temperature in hot QCD

TL;DR

This paper investigates how shear viscosity in hot QCD is suppressed near the critical temperature, revealing a significant decrease in eta/T^3 and the viscosity-to-entropy ratio as the system approaches the deconfinement transition.

Contribution

It demonstrates that shear viscosity is suppressed by the Polyakov loop near the critical temperature, highlighting the semi-QGP phase's properties.

Findings

Shear viscosity eta is suppressed by two powers of the Polyakov loop.

The ratio of shear viscosity to entropy becomes small near Tc.

eta/T^3 decreases markedly as temperature approaches Tc.

Abstract

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 ,eta, is suppressed by two powers of the Polyakov loop. This suggests that eta/T^3 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.