Bulk viscosity in the nonlinear and anharmonic regime of strange quark matter

TL;DR

This paper investigates how bulk viscosity in strange quark matter varies with temperature and oscillation amplitude, including effects of anharmonic oscillations, revealing mostly small quantitative impacts except at very large amplitudes.

Contribution

It extends the analysis of bulk viscosity to include nonlinear and anharmonic density oscillations, highlighting qualitative effects with minimal quantitative change.

Findings

Anharmonicity causes qualitative effects in bulk viscosity.

Nonlinear effects are small for oscillation amplitudes below 10%.

Most processes are unaffected by anharmonicity at moderate amplitudes.

Abstract

The bulk viscosity of cold, dense three-flavor quark matter is studied as a function of temperature and the amplitude of density oscillations. The study is also extended to the case of two different types of anharmonic oscillations of density. We point several qualitative effects due to the anharmonicity, although quantitatively they appear to be relatively small. We also find that, in most regions of the parameter space, with the exception of the case of a very large amplitude of density oscillations (i.e. 10% and above), nonlinear effects and anharmonicity have a small effect on the interplay of the nonleptonic and semileptonic processes in the bulk viscosity.