AI 中文总结
本研究利用两味夸克-介子模型计算有限温密下QCD拓扑荷六阶累积量$b_4$与轴子六次自耦合，验证其真空与高温高密行为，揭示临界点发散与相变符号翻转特性，并分析自由能泰勒展开的收敛性。
AI 中文摘要
我们在包含和不包含Polyakov-loop（波利雅科夫圈）动力学的两味夸克-介子（QM）模型框架内，计算了有限温度$T$和重子化学势$\u03bc$下QCD拓扑荷分布的六阶累积量$b_4$，以及轴子的六次自耦合。真空中的$b_4$处于格点SU(3)纯规范模拟预测的范围内，在高$T$和/或高$\u03bc$下，它趋近于稀薄瞬子气体近似所预测的常数。$b_4$和轴子六次自耦合均在QCD临界点处发散，且在相变两侧符号翻转。我们通过与平均场水平的全势对比，研究了作为$\u03b8$参数函数的自由能的四阶和六阶泰勒展开的收敛性。
英文摘要
The sixth-order cumulant $b_4$ of the QCD topological charge distribution and the axion's sextic self-coupling at finite temperature $T$ and baryon chemical potential $μ$ are calculated within the two-flavor quark-meson (QM) model without and with the Polyakov-loop dynamics. The $b_4$ in the vacuum falls within the range predicted by lattice SU(3) pure-gauge simulations, and at large $T$ and/or $μ$, it tends to a constant predicted by the dilute instanton gas approximation. Both $b_4$ and the axion's sextic self-coupling diverge at the QCD critical point and flip sign across the phase transition. The convergence of the fourth- and sixth-order Taylor expansions of the free energy as a function of the $θ$ parameter is investigated via comparison with the full potential at the mean-field level.
Comments17 pages, 17 figures,
