Transport Coefficients from pQCD to the Hadron Resonance Gas at finite BSQ densities

TL;DR

This paper calculates shear viscosity in QCD and hadron resonance gas models at finite baryon, strangeness, and charge densities, using perturbative and non-perturbative approaches and connecting these regimes through an interpolation framework.

Contribution

It introduces an interpolation method connecting perturbative QCD and hadron resonance gas shear viscosities at finite BSQ densities, including near NLO weak-coupling results.

Findings

Shear viscosity computed in both QCD and HRG regimes.

Interpolation successfully connects the two regimes at finite densities.

Discussion on convergence of the perturbative series.

Abstract

We calculate the shear viscosity, $\eta$, in two limits: perturbative QCD and an excluded-volume hadron resonance gas (HRG), at finite BSQ densities. Using an interpolation framework, we connect these regimes. In addition, we present results for (almost) next-to-leading order weak-coupling shear viscosity for QCD at finite $\mu_B$, and discuss the convergence of the perturbative series.