Shear viscosity from Kubo formalism: NJL-model study

Abstract

A large-$N_{\mathrm{c}}$ expansion is combined with the Kubo formalism to study the shear viscosity $\eta$ of strongly interacting matter in the two-flavor NJL model. We discuss analytical and numerical approaches to $\eta$ and investigate systematically its strong dependence on the spectral width and the momentum-space cutoff. Thermal effects on the constituent quark mass from spontaneous chiral symmetry breaking are included. The ratio $\eta /s$ and its thermal dependence are derived for different parameterizations of the spectral width and for an explicit one-loop calculation including mesonic modes within the NJL model.

Comments: 14 pages, 11 figures. Revision includes additionally the spectral width at one-loop level (chapter V) and Appendix A. Matches published version