Hot and Dense QCD Shear Viscosity at (almost) NLO

TL;DR

This paper extends the calculation of QCD shear viscosity at next-to-leading order to finite baryon chemical potential, revealing improved convergence at high chemical potential, relevant for heavy ion collisions and neutron star mergers.

Contribution

The authors generalize NLO shear viscosity calculations to finite chemical potential, addressing a gap in applying weak-coupling results to realistic astrophysical and experimental conditions.

Findings

Weak-coupling expansion convergence improves at high chemical potential.

Finite $mbda$ calculations are feasible and relevant for dense QCD matter.

Results suggest applicability limits of weak-coupling methods in dense regimes.

Abstract

The next-to-leading order weak-coupling shear viscosity of QCD was computed 6 years ago. However, these results have never been applied at finite baryon chemical potential $\mu$, even though intermediate-energy heavy ion collisions and merging neutron stars may explore the Quark-Gluon Plasma in a regime where baryon chemical potentials are large. Here, we extend the next-to-leading order shear viscosity calculations to finite $\mu$, and we show that, while the convergence of the weak-coupling expansion is questionable for achievable plasmas, it is somewhat better at $\mu > T$ than at $\mu=0$.