Abstract
We study the diffusion properties of the strongly interacting quark-gluon plasma (sQGP) and evaluate the diffusion coefficient matrix for the baryon (B), strange (S) and electric (Q) charges---${\ensuremath{\kappa}}_{q{q}^{\ensuremath{'}}}$ ($q,{q}^{\ensuremath{'}}=\mathrm{B},\mathrm{S},\mathrm{Q}$) and show their dependence on temperature $T$ and baryon chemical potential ${\ensuremath{\mu}}_{\mathrm{B}}$. The nonperturbative nature of the sQGP is evaluated within the dynamical quasiparticle model (DQPM) which is matched to reproduce the equation of state of the partonic matter above the deconfinement temperature ${T}_{c}$ from lattice QCD. The calculation of diffusion coefficients is based on two methods: (i) the Chapman-Enskog method for the linearized Boltzmann equation, which allows to explore nonequilibrium corrections for the phase-space distribution function in leading order of the Knudsen numbers as well as (ii) the relaxation time approximation (RTA). In this work we explore the differences between the two methods. We find a good agreement with the available lattice QCD data in case of the electric charge diffusion coefficient (or electric conductivity) at vanishing baryon chemical potential as well as a qualitative agreement with the recent predictions from the holographic approach for all diagonal components of the diffusion coefficient matrix. The knowledge of the diffusion coefficient matrix is also of special interest for more accurate hydrodynamic simulations.
Highlights
An exploration of the properties of hot and dense matter—created in heavy-ion collisions (HICs) at relativistic energies—is the focus of extensive research
We find a good agreement with the available lattice QCD data in case of the electric charge diffusion coefficient at vanishing baryon chemical potential as well as a qualitative agreement with the recent predictions from the holographic approach for all diagonal components of the diffusion coefficient matrix
In the recent past we have addressed the coupling of the conserved baryon number, strangeness and electric charge; the diffusion coefficient matrix was introduced and evaluated for a hadron gas and a simple model for quark-gluon plasma (QGP) [15,17]
Summary
An exploration of the properties of hot and dense matter—created in heavy-ion collisions (HICs) at relativistic energies—is the focus of extensive research. In the recent past we have addressed the coupling of the conserved baryon number, strangeness and electric charge; the diffusion coefficient matrix (κqq0, where q; q0 1⁄4 B; S; Q) was introduced and evaluated for a hadron gas and a simple model for quark-gluon plasma (QGP) [15,17] These investigations were followed by a more extended study in the hadronic phase from kinetic theory in the case of the electric cross-conductivities [19]. [15,17,18] and evaluate the diffusion coefficient matrix of the strongly interacting nonperturbative QGP at finite (T; μB), with properties described by the DQPM model, based on recently explored the ChapmanEnskog method [15,17,40] This allows us to explore the influence of traces of nonequilibrium effects by accounting for the higher modes of the distribution function on the transport properties and compare the results with the often used kinetic RTA approximation. We provide and discuss improved results for all diffusion coefficients and conductivities and compare them to the available results from other approaches
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