Shear viscosity of nuclear matter

Abstract

Shear viscosity $\eta$ is calculated for the nuclear matter described as a system of interacting nucleons with the van der Waals (VDW) equation of state. The Boltzmann-Vlasov kinetic equation is solved in terms of the plane waves of the collective overdamped motion. In the frequent-collision regime, the shear viscosity depends on the particle-number density $n$ through the mean-field parameter $a$, which describes attractive forces in the VDW equation. In the temperature region $T=15-40$~MeV, a ratio of the shear viscosity to the entropy density $s$ is smaller than 1 at the nucleon number density $n=(0.5-1.5)n_0^{}$, where $n_0^{}=0.16$fm${}^{-3}$ is the particle density of equilibrium nuclear matter at zero temperature. A minimum of the $\eta /s$ ratio takes place somewhere in a vicinity of the critical point of the VDW system. Large values of $\eta /s\gg 1$ are, however, found in both the low-density, $n\ll n_0^{}$, and high-density, $n>2n_0^{}$, regions. This makes the ideal hydrodynamic approach inapplicable for these densities.

Comments: 12 pages, 5 figures