https://doi.org/10.1140/epja/i2015-15127-7
Regular Article - Theoretical Physics
Shear viscosities from Kubo formalism in a large-Nc Nambu-Jona-Lasinio model
1
Physik Department, Technische Universität München, D-85747, Garching, Germany
2
ECT, Villa Tambosi, I-38123, Villazzano (TN), Italy
* e-mail: robert.lang@ph.tum.de
Received:
15
June
2015
Revised:
8
September
2015
Accepted:
11
September
2015
Published online:
16
October
2015
In this work the shear viscosity of strongly interacting matter is calculated within a two-flavor Nambu-Jona-Lasinio model as a function of temperature and chemical potential. The general Kubo formula is applied, incorporating the full Dirac structure of the thermal quark spectral function and avoiding commonly used on-shell approximations. Mesonic fluctuations contributing via Fock diagrams provide the dominant dissipative processes. The resulting ratio η/s (shear viscosity over entropy density) decreases with temperature and chemical potential. Interpolating between our NJL results at low temperatures and hard thermal loop results at high temperatures a minimum slightly above the AdS/CFT benchmark η/s = 1/4τ is obtained.
© SIF, Springer-Verlag Berlin Heidelberg, 2015
