标题： 大N QCD的热力学及亚稳相的本质 显示英文标题

标题： The thermodynamics of large-N QCD and the nature of metastable phases

摘要： 在大颜色数（N）的极限下，Yang-Mills 理论和量子色动力学都被认为有一个一阶相变，分离出一个禁闭的手征相和一个去禁闭的等离子相。这种分离的一个方面是，在大 N 时，可以明确识别出一个强耦合的等离子区域。一阶相变的存在表明手征相可以过热，而等离子相可以过冷。在大 N 下存在的过冷去禁闭等离子体，如果存在的话，具有一个显著的性质，即它具有负绝对压强——也就是说，比真空压强还低的压强。对于 1/N 展开中密度约为 1 的能量密度，但在手征过热相的终点之后，存在一种由普通质量约为 1 的手征粒子组成的均匀物质的描述，且表现得好像温度为$T_H$。然而，正则系综和微观系综描述之间的联系破裂，并且系统不能完全达到平衡状态$N \rightarrow \infty$。相反，在手征粒子描述中，能量被推向质量任意大的手征粒子。对于这些系统，大体积的热力学极限变得微妙：能量密度不再是强度量。只要标准的大 N 尺度规则成立，大 N 下的系统经历手征相和等离子相之间的一般一阶相变，并且介子和胶球遵循 Hagedorn 型谱系，这些结论就会成立。 显示英文摘要

摘要： In the limit of a large number of colors (N), both Yang-Mills and quantum chromodynamics are expected to have a first-order phase transition separating a confined hadronic phase and a deconfined plasma phase. One aspect of this separation is that at large N, one can unambiguously identify a plasma regime that is strongly coupled. The existence of a first-order transition suggests that the hadronic phase can be superheated and the plasma phase supercooled. The supercooled deconfined plasma present at large N, if it exists, has the remarkable property that it has negative absolute pressure -- i.e. a pressure below that of the vacuum. For energy densities of order unity in a 1/N expansion but beyond the endpoint of the hadronic superheated phase, a description of homogeneous matter composed of ordinary hadrons with masses of order unity in a 1/N expansion can exist, and acts as though it has a temperature of $T_H$ in order unity. However, the connection between the canonical and microcanonical descriptions breaks down and the system cannot fully equilibrate as $N \rightarrow \infty$. Rather, in a hadronic description, energy is pushed to hadrons with masses that are arbitrarily large. The thermodynamic limit of large volumes becomes subtle for such systems: the energy density is no longer intensive. These conclusions follow provided that standard large N scaling rules hold, the system at large N undergoes a generic first-order phase transition between the hadronic and plasma phases and that the mesons and glueballs follow a Hagedorn-type spectrum.