The multiplicity distributions of net-baryon number fluctuation in the first-order chiral phase transition associated with the nonequlibrium effect are investigated within the improved Polyakov–Nambu–Jona–Lasinio model. Compared with the idealized first-order transition in equilibrium, the calculation indicates that the density fluctuations in the metastable and unstable regions are more violent, which possibly affects the statistical distributions of density fluctuation in later stage of an expanding system. Signals induced by the first-order phase transition and those from the nonequilibrium effect are discussed in detail, which could be exploited to identify the first-order phase transition. Besides, the critical exponents of the thermodynamic quantities at both the critical end point and spinodal boundary are investigated.

中文翻译：

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QCD物质的波动，临界和非平衡效应

在改进的Polyakov–Nambu–Jona–Lasinio模型中，研究了与非平衡效应相关的一阶手性相变中净重子数波动的多样性分布。与理想的平衡一阶跃迁相比，计算表明亚稳和不稳定区域的密度波动更为剧烈，这可能会影响扩展系统后期密度波动的统计分布。详细讨论了由一阶相变引起的信号和非平衡效应引起的信号，这些信号可用于识别一阶相变。此外，还研究了临界点和旋节线边界处的热力学量的临界指数。