QCD at finite chemical potential in and out-of equilibrium

TL;DR

This paper reviews the transport properties of the quark-gluon plasma in and out of equilibrium, comparing theoretical models with experimental observables to understand its behavior at different temperatures and chemical potentials.

Contribution

It provides a comprehensive comparison of equilibrium and out-of-equilibrium transport properties of the QGP using the DQPM model and microscopic transport simulations.

Findings

Transport coefficients vary with temperature and chemical potential.

The DQPM reproduces lattice QCD results for the equation of state.

Certain observables are sensitive indicators of QGP formation.

Abstract

We review the transport properties of the strongly interacting quark-gluon plasma (QGP) created in heavy-ion collisions at ultrarelativistic energies, i.e. out-of equilibrium, and compare them to the equilibrium properties. The description of the strongly interacting (non-perturbative) QGP in equilibrium is based on the effective propagators and couplings from the Dynamical QuasiParticle Model (DQPM) that is matched to reproduce the equation-of-state of the partonic system above the deconfinement temperature $T_c$ from lattice QCD. We study the transport coefficients such as the ratio of shear viscosity and bulk viscosity over entropy density, diffusion coefficients, electric conductivity etc. versus temperature and baryon chemical potential. Based on a microscopic transport description of heavy-ion collisions we, furthermore, discuss which observables are sensitive to the QGP formation and its properties.