极端条件下的手征恢复和退禁闭相变及可能的新物质形态

Quarkyonic matter is a theoretically predicted QCD state, which possibly exhibits in a low temperature but high baryon density region. It is characterized by the chiral symmetry restored but color confined quarks. Of its particular interest, the laboratories of CBM at FAIR, NICA at JINR and CSR at HIRFL, all they are planning to identify the existence of quarkyonic matter since such cold, dense phase will onset in their future colliding heavy ion systems. In the frame of thermal field theory, we will calculate the thermal photon (gluon) polarization tensor in an external magnetic field and then deduce the effective Polyakov loop potential from the hard loop corrected gluon and ghost propagators. Comparing with the lattice data, it is allowed us to construct an extended PNJL model via fitting a set of parameters, which depend on the temperatures as well as magnetic fields. After that, we will employ these parameters to the high-density environment, which is a regime lacking of lattice data. Under the help of this model, our further works will expand into three parts. The first problem is to explore the existence of quarkyonic matter. The second one is to calculate the transport coefficients of QCD matter at finite temperatures and densities. Finally, we will be dedicated to proposing the signature observables in the experiments. Our project focuses on a new probable QCD phase creating in the next heavy ion collisions. It is not only a theoretical investigation in phase diagram of QCD but also will shed a light on the preparations of heavy-ion collider facilities.

夸克素物质是指核物质在低温高密区域可能存在的一种新物质形态，其主体成分是手征对称性恢复但仍处于色禁闭的夸克。在未来 CBM、NICA 和 CSR 能区实验中的核核碰撞中心区域，可形成相对低温高密的环境具有产生夸克素态的条件。本课题的主要工作就是基于温度场论计算强磁场下胶子和鬼传播子的理论形式并由此计算 Polyakov loop 有效势。通过和格点 QCD 的数据拟合，确定构造 PNJL 模型所需参数及其对温度和磁场的依赖行为，然后推广至高密区域。由此摆脱在高密时缺乏格点数据的困境，建立一个参数可信的 PNJL 模型。 由此探讨夸克素物质是否存在这一物理课题。我们还将计算低温高密时 QCD 物质的输运系数，并预测实验上判别夸克素物质是否存在的特征观测量。研究重离子碰撞实验中可能形成的新物质形态，这既是对 QCD 相图结构这一前沿基础科学进行探索，也为将来重离子碰撞实验的信号探测提供指导。

本课题主要研究了夸克物质在电磁场下具有不同于温度的物质结构相图。我们推广 Schwigher Proper Time 方法到两味空间，成功的在夸克模型下计算了带电 pion 凝聚随着电磁场变化的相变过程。当同位旋足够大时，它将催化强互作用物质从 sigma 道到带电 pion 道凝聚的转变。但是由于外电磁场下带电粒子的传播子变得极其复杂，超出点粒子模型来研究带电 pion 介子一直是个理论难点。而我们成功的解析得到夸克的两点格林函数，进而计算了系统热力学势随电磁场变化的行为。我们的解析结果表明此时热力学势含有六次方项。因此，其相应的手征恢复是一个一级相变。两色强相互作用物质具有两倍拓展的味道空间，可同时研究介子和双夸克态，即重子。在外电磁场环境中，电磁反常可用赝标同位化学势进行简单替换。在高密夸克物质中，我们发现赝标同位化学势可导致自旋为一的赝矢量双夸克凝聚。我们同时使用了手征微扰理论和 Nambu--Jona-Lasinio 模型计算了系统的有效热力学势。数值计算表明，相比于传统的标量双夸克凝聚，这种新的双夸配对方式将改变中微子逃逸系数，更好地符合现今已观测到的中子星冷却行为。