dorsal/arxiv
View SchemaBulk viscosity of quark matter across the QCD phase transitions
| Authors | Chong-long Xie, Guo-yun Shao, Ming-zheng-xuan Wu, Wei-bo He |
|---|---|
| Categories | |
| ArXiv ID | 2601.10126vv1 |
| URL | https://arxiv.org/abs/2601.10126 |
| License | http://creativecommons.org/licenses/by/4.0/ |
Abstract
Based on the kinetic theory with relaxation time approximation, we investigate the bulk viscosity ($\zeta$) and its ratio to shear viscosity ($\zeta/\eta$) of quark matter at finite temperature and chemical potential with the in-medium particle masses derived in the 2+1 flavor Polyakov-loop improved Nambu--Jona-Lasinio (PNJL) model. We explore the behaviors of specific bulk viscosity ($\zeta/s$) and $\zeta/\eta$ across different QCD phase transitions, including the Mott phase transition, the chiral crossover, and the first-order transition with the associated metastable phase. The calculation shows that both $\zeta/s$ and $\zeta/\eta$ are extremely small at high temperatures, approaching the nature of a conformal theory. Larger $\zeta/s$ and $\zeta/\eta$ are derived near the chiral phase transition at finite temperature. Along the chiral crossover line, $\zeta/s$ and $\zeta/\eta$ generally increase with decreasing temperature, though $\zeta/\eta$ exhibits a slight decline near the critical endpoint (CEP). On the boundary of the first-order transition, $\zeta/s$ shows a non-monotonic variation with temperature. Furthermore, an additional peak structure emerges beyond the chiral phase boundary for both $\zeta/s$ and $\zeta/\eta$, with magnitudes even exceeding those near the chiral crossover of $u, d$ quarks. Our analysis indicates this peak originates from the chiral crossover transformation of strange quark.
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"abstract": "Based on the kinetic theory with relaxation time approximation, we investigate the bulk viscosity ($\\zeta$) and its ratio to shear viscosity ($\\zeta/\\eta$) of quark matter at finite temperature and chemical potential with the in-medium particle masses derived in the 2+1 flavor Polyakov-loop improved Nambu--Jona-Lasinio (PNJL) model. We explore the behaviors of specific bulk viscosity ($\\zeta/s$) and $\\zeta/\\eta$ across different QCD phase transitions, including the Mott phase transition, the chiral crossover, and the first-order transition with the associated metastable phase. The calculation shows that both $\\zeta/s$ and $\\zeta/\\eta$ are extremely small at high temperatures, approaching the nature of a conformal theory. Larger $\\zeta/s$ and $\\zeta/\\eta$ are derived near the chiral phase transition at finite temperature. Along the chiral crossover line, $\\zeta/s$ and $\\zeta/\\eta$ generally increase with decreasing temperature, though $\\zeta/\\eta$ exhibits a slight decline near the critical endpoint (CEP). On the boundary of the first-order transition, $\\zeta/s$ shows a non-monotonic variation with temperature. Furthermore, an additional peak structure emerges beyond the chiral phase boundary for both $\\zeta/s$ and $\\zeta/\\eta$, with magnitudes even exceeding those near the chiral crossover of $u, d$ quarks. Our analysis indicates this peak originates from the chiral crossover transformation of strange quark.",
"arxiv_id": "2601.10126",
"authors": [
"Chong-long Xie",
"Guo-yun Shao",
"Ming-zheng-xuan Wu",
"Wei-bo He"
],
"categories": [
"hep-ph"
],
"license": "http://creativecommons.org/licenses/by/4.0/",
"title": "Bulk viscosity of quark matter across the QCD phase transitions",
"url": "https://arxiv.org/abs/2601.10126",
"version": "v1"
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