Transport coefficients of the Gribov-Zwanziger plasma

Abstract

We study dynamic features of a plasma consisting of gluons whose infrared dynamics is improved by the Gribov-Zwanziger quantization. This approach embodies essential features of color confinement which set the plasma apart from conventional quasiparticle systems in several aspects. Our study focusses on a boost-invariant expansion for in- and out-of-equilibrium settings, which at late times can be characterized by the sound velocity, $c_s$, and the shear, $\eta$, and bulk, $\zeta$, viscosities. We obtain explicit expressions for the transport coefficients $\eta$ and $\zeta$ and check that they are consistent with the numerical solutions of the kinetic equation. At high temperature, keeping both the Gribov parameter and the relaxation time constant, we find a scaling $\zeta /\eta \propto 1/3-c_s^2$ which manifests strong breaking of conformal symmetry in contrast to the case of weakly coupled plasmas.

Comments: 21 pages, 11 figures, minor changes: results obtained with momentum-dependent relaxation time are corrected, conclusions unmodified