2020/07/31 by Valeriya Mykhaylova, Chihiro Sasaki
Physics and Astronomy · #Chiral perturbation theory #Condensed matter physics #High-Energy Particle Collisions Research #Lattice QCD #Particle physics #Particle physics theoretical and experimental studies #Phase transition #Physics #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #Quantum electrodynamics #Quark #Quark–gluon plasma #Quasiparticle #Thermodynamics #Viscosity #Volume viscosity #hep-ph
paper · pdf · doi:10.1103/physrevd.103.014007
published as Phys. Rev. D 103, 014007 (2021) · The version accepted for publication in Phys. Rev. D
arxiv created 2020/12/01 · openalex publication_date 2021/01/08 · arxiv updated 2021/01/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We study the bulk and shear viscosity and the electrical conductivity in a quasiparticle approach to Yang--Mills theory and QCD with light and strange quarks to assess the dynamical role of quarks in transport properties at finite temperature. The interactions with a hot medium are embodied in effective masses of the constituents through a temperature-dependent running coupling extracted from the lattice QCD thermodynamics. In Yang--Mills theory, the bulk viscosity to entropy density ratio exhibits a nonmonotonous structure around the phase transition temperature. In QCD, this is totally dissolved because of a substantial contribution from quark quasiparticles. The bulk to shear viscosity ratio near the phase transition behaves consistently to the scaling with the speed of sound derived in the AdS/CFT approach, whereas at high temperature it obeys the same parametric dependence as in perturbation theory. Thus, the employed quasiparticle model is adequate to capture the transport properties in the weak and strong coupling regimes of the theory. This feature is not altered by including dynamical quarks which, however, retards the system from restoring conformal invariance. We also examine the individual flavor contributions to the electrical conductivity and show that the obtained behavior agrees qualitatively well with the recent results of lattice simulations and with a class of phenomenological approaches.