Fermi-liquid view of viscosity in cold and dense nucleon matter

TL;DR

This paper develops a Fermi-liquid theoretical framework to calculate shear and bulk viscosities in cold, dense nucleon matter, providing analytical expressions and numerical results relevant for nuclear physics experiments.

Contribution

It introduces a relativistic kinetic theory approach with medium-dependent quasiparticles and couples it to a mean-field equation of state for nucleon matter, extending previous work.

Findings

Bulk viscosity is nonnegative due to Landau matching.

Derived leading-order temperature dependence of viscosities in the degenerate regime.

Calculated viscosities for nucleon matter relevant to nuclear experiments.

Abstract

We develop a framework to calculate transport properties in cold, dense relativistic quasiparticle system within the Fermi-liquid theory at the mean-field level. Building on our previous study [Phys. Rev. C 111, 044904 (2025)], we start from the linearized relativistic Boltzmann equation tailored to quasiparticles with medium-dependent dispersion relation and implement Landau matching conditions, proving that the bulk viscosity is manifestly nonnegative. A low-temperature expansion then yields leading-order ($T/\mu^*$) expressions for the shear ($\eta$) and bulk ($\zeta$) viscosities, where the behavior $\zeta/\eta \propto (T/\mu^*)^4$ in the degenerate regime is found to be robust against quasiparticle mass correction. We couple the kinetic framework to a Walecka-type mean-field equation of state and compute $\eta$ and $\zeta$ for cold, dense nucleon matter. The transport properties of nucleonic matter in the degenerate regime can be relevant for intermediate beam-energy nuclear experiments.