PNJL模型下手征相变的临界指数

在PNJL模型下研究了临界点和旋节线边界上的临界指数。计算表明四个标准的临界指数$\alpha,\,\beta,\,\gamma,\,\delta$在 平均场近似下与朗道-金斯堡理论的预言一致。重子数涨落分布峰态的临界指数$\eta(\approx2)$大于偏态的 临界指数$\zeta(\approx1)$，这表明，如果在重离子碰撞实验中可以达到临界区域，峰态的测量比偏态的测量更加敏感。计算结果还表明，偏态(峰态)在旋节线边界上的临界指数与在临界点的临界指数具有相同的发散强度。根据重子数在不稳定相和亚稳相的剧烈涨落及峰态和偏态在旋节线边界上发散的特点，在将来的实验中用于鉴别一阶相变的信号在一定程度上会被干扰，一些偏离标准一阶相变的信号或许会在观测中发现。

Critical Exponents of the Chiral Phase Transition in the PNJL Model

The critical exponents at the Critical end Point(CEP) and the spinodal boundaries are investigated in the Poyakov-Nambu--Jona-Lasinio(PNJL) model. The numerical results show that the four standard critical exponents, $\alpha, \beta, \gamma$ and $\delta$, are consistent with Landau-Ginzburg theory in the mean-field approximation. The critical exponent $\eta ~(\approx2)$ correlated to kurtosis is larger than the critical exponent $\zeta~(\approx1)$ of skewness at the CEP, which indicates that the measurement of kurtosis is more sensitive than skewness if the critical region can be reached in heavy-ion collision. The calculation also shows that the critical exponent of skewness~(kurtosis) along the spinodal line has the same divergent strength as that at the CEP. Due to the violent fluctuations in the unstable and metastable phases and the divergence of skewness and kurtosis at the spinodal boundaries, the signals to identify the first-order transition in the future experiments will be disturbed to a certain degree. Some deviations from the prediction of standard first-order transition may be found in observation.