Thermal Transport and Drag Force in Improved Holographic QCD

Abstract

We calculate the bulk viscosity, drag force and jet quenching parameter in Improved Holographic QCD. We find that the bulk viscosity rises near the phase transition but does not exceed the shear viscosity. The drag force shows the effects of asymptotic freedom both as a function of velocity and temperature. It indicates diffusion times of heavy quarks in rough agreement with data. The jet quenching parameter values computed via the light-like Wilson loop are in the lower range suggested by data.

Comments: Latex, 61 pages, 18 eps figures. Published version: bulk viscosity section expanded, discussion improved, 2 appendices added; v3: minor mistakes corrected; v4: mistake in eq. (4.21) corrected.