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arXiv · 1506.02459

Shear Viscosities from Kubo Formalism in a large-$N_{\rm c}$ Nambu--Jona-Lasinio Model

Robert Lang·Norbert Kaiser·Wolfram Weise
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Abstract

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 $\eta/s$ (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 $\eta/s=1/4\pi$ is obtained.

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Robert Lang, Norbert Kaiser, Wolfram Weise. 2015-06-08. Shear Viscosities from Kubo Formalism in a large-$N_{\rm c}$ Nambu--Jona-Lasinio Model. https://doi.org/10.1140/epja/i2015-15127-7

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