Hot QCD: transport coefficients in strong and weak coupling regimes
Abstract
We evaluate the transport coefficients, namely the shear viscosity η and the spatial diffusion coefficient of heavy quarks Ds, within a Quasi-Particle Model (QPM). In particular, for the first time this has been done by exploiting novel lQCD data at Nf=3+1. In such a framework, in which the gluons are massive, the interactions among quarks and gluons have been evaluated via the scattering matrices evaluated from tree level Feynman diagrams. As far as the evaluation of Ds is concerned, the Fokker-Planck approximation for the relativistic Boltzmann equation has been employed for the diffusion of both charm and bottom quarks in either a Nf=3 and a Nf=3+1 bulk. We have developed a dual-component Chapman-Enskog formalism for the ratio η/s (being s the entropy density) of a mixture of quarks and gluons. The temperature dependence of the shear viscosity is then compared to the results from a Green-Kubo approach, based on the numerical resolution of the relativistic Boltzmann equation with a stochastic implementation of the collision integral. Finally, using the above results, we compare the strong and weak coupling regimes for the ratio (2πT Ds)/(4πη/s).
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BibTeX
@misc{parisi2026transport,
title = {{Hot QCD: transport coefficients in strong and weak coupling regimes}},
author = {Gabriele Parisi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.08521},
eprint = {2609.08521},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.08521},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Hot QCD: transport coefficients in strong and weak coupling regimes
AU - Gabriele Parisi
PY - 2026
DA - 2026/09/08
PB - arXiv
DO - 10.48550/arxiv.2609.08521
UR - https://arxiv.org/abs/2609.08521
AB - We evaluate the transport coefficients, namely the shear viscosity η and the spatial diffusion coefficient of heavy quarks D_s, within a Quasi-Particle Model (QPM). In particular, for the first time this has been done by exploiting novel lQCD data at N_f=3+1. In such a framework, in which the gluons are massive, the interactions among quarks and gluons have been evaluated via the scattering matrices evaluated from tree level Feynman diagrams. As far as the evaluation of D_s is concerned, the Fokker-Planck approximation for the relativistic Boltzmann equation has been employed for the diffusion of both charm and bottom quarks in either a N_f=3 and a N_f=3+1 bulk. We have developed a dual-component Chapman-Enskog formalism for the ratio η/s (being s the entropy density) of a mixture of quarks and gluons. The temperature dependence of the shear viscosity is then compared to the results from a Green-Kubo approach, based on the numerical resolution of the relativistic Boltzmann equation with a stochastic implementation of the collision integral. Finally, using the above results, we compare the strong and weak coupling regimes for the ratio (2πT D_s)/(4πη/s).
ER -