标题： 声速在手征交叉处的QCD物质 显示英文标题

标题： Speed of sound of QCD matter at chiral crossover

摘要： 基于一种由簇分解启发的QCD热力学广义Bethe-Uhlenbeck方法，我们提出了一种热强相互作用物质的统一状态方程，并在其广泛温度范围内的性质进行了分析。 强子在介质中被处理为带有背景胶子场的色单态多夸克簇，在Polyakov规范下。 QCD的约束特性通过Polyakov环机制以及由约束密度泛函方法提出的较大真空夸克质量来体现。 我们证明了强子和部分子自由度之间的突然转换，这是手征对称性动态恢复的一个显著表现，伴随着手征转变时熵密度的平滑行为。 首次分析了强相互作用物质不同成分对其声速的单独贡献。 结果表明，手征对称性的恢复会使强子气体的声速降至负值，表现出其机械不稳定，这与格点QCD数据存在明显矛盾。 考虑部分子激发自然地解决了这一矛盾。 显示英文摘要

摘要： Based on a generalized Beth-Uhlenbeck approach to thermodynamics of QCD motivated by cluster decomposition we present a unified equation of state of hot strongly interacting matter and analyze its properties in a wide range of temperatures. The hadrons are treated as color singlet multiquark clusters in medium with a background gluon field in the Polyakov gauge. The confining aspect of QCD is accounted for by the Polyakov loop mechanism and by a large vacuum quark mass motivated by a confining density functional approach. We demonstrate that an abrupt switching between hadronic and partonic degrees of freedom, which is one of striking manifestations of dynamical restoration of chiral symmetry, is accompanied by a smooth behavior of entropy density at chiral crossover. Individual contributions of different components of strongly interacting matter to its speed of sound are analyzed for the first time. It is shown that restoration of chiral symmetry drives speed of sound of hadron gas to negative values, manifesting its mechanical instability and being in a strike disagreements with the lattice QCD data. Accounting for the partonic excitations naturally resolves this contradiction.