Eur. Phys. J. A (2014) 50: 63
https://doi.org/10.1140/epja/i2014-14063-4

Regular Article - Theoretical Physics

Shear viscosity from Kubo formalism: NJL model study

¹ Physik Department, Technische Universität München, D-85747, Garching, Germany
² Theoretical Research Division, Nishina Center, RIKEN, 351-0198, Wako, Japan
³ ECT*, Villa Tambosi, I-38123, Villazzano (TN), Italy

^* e-mail: robert.lang@ph.tum.de

Received: 19 November 2013
Revised: 7 February 2014
Accepted: 22 February 2014
Published online: 26 March 2014

Abstract

A large-N _c expansion is combined with the Kubo formalism to study the shear viscosity η of strongly interacting matter in the two-flavor NJL model. We discuss analytical and numerical approaches to η 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 η/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.