Dynamics of the quark-gluon plasma and high density hadronic matter

1我们用最大熵方法在欧几里德格点上测量了由粲夸克对和反粲夸克对构成的矢量（J/π）和轴矢量（η_c）通道的相关函数，构造了它们在有限温度下的谱函数，并首次将其系统地应用于格点规范理论。结果表明，这两种态在远高于QCD相变温度（约1.6T_c）的温度范围内继续存在，并在1.6T_c ~ 1.7T_c的一个很窄的温度范围内消失。这表明夸克胶子等离子体并不是通常认为的夸克胶子几乎自由运动的状态。但它是一个强耦合系统，其中强子激发也共存。2有人认为，在QCD相图上可能存在一个临界端点，其中相变的顺序从第一次转变到交叉。我们在相变理论的普适性假设的基础上导出了具有临界终点的一般状态方程，发现它在系统的时间演化过程中起着吸引子的作用。在此基础上，我们首次在统一的框架下讨论了高能重离子碰撞产生的系统在时间演化过程中通过临界终点附近时的涨落和关联长度的时间演化及其对观测量的影响。

1 We have constructed the spectral functions at finite temperature for the vector (J/ψ) and axial-vector (η_c) channels made of a charm and anti-charm quark pair from their correlation functions measured on the Euclidean lattices with the maximum entropy method, which was applied systematically to lattice gauge theory for the first time by our group. It was shown that both states continue to exist up to a temperature that is much higher than the QCD phase transition temperature, that is, about 1.6T_c and that they both disappears in a very narrow temperature region, between about 1.6T_c and 1.7T_c This suggests that the quark-gluon plasma is not a state where quarks and gluons are almost freely moving as usually believed, but that it is a strongly coupled system where also hadronic excitations coexists.2 It has been argued that there is possibly a critical end point on the QCD phase diagram, where the order of the phase transition changes from first to crossover We have derived general equations of states with a critical end point on the basis of the universality hypothesis in phase transition theory and found that it acts as an attractor in the course of the time evolution of the system. Furthermore, we discussed for the first time the time evolution of fluctuations and correlation lengths when the system created in high energy heavy ion collisions pass the proximity of the critical end point in the course of its time evolution and their effects on observables in a unified framework.