标题： 宇称双重模型的热力学：不对称物质和中子物质 显示英文标题

标题： Thermodynamics of the parity-doublet model: Asymmetric and neutron matter

摘要： 我们在扩展平均场计算中考虑了偶数模型中的同位旋不对称物质，并不断增加中子过剩量直至纯中子物质。 我们计算了零至适度温度下发生的液气相变和手征相变，但特别关注零温及大重子密度下物质的相结构。 自由能的计算涉及间隙方程的求解。 这是通过将这些间隙方程转化为控制各种物理量（标量凝聚态、质子和中子密度及其各自的手征伙伴密度）随重子密度增加而流动的常微分方程实现的。 在这种表述中，微分方程的初始条件决定了整个相结构。 进一步证明了手征伙伴开始占据的阈值完全由费米子参数决定，尤其是核子的手征不变质量。 我们强调了宇称对称能量在驱动核子及其宇称伙伴在手征转变过程中达到平衡的作用。 我们详细分析了当改变中子过剩量时物质性质的变化，包括对手征极限的特殊讨论，并系统地比较了偶数模型与其对应的单数模型，其中核子的手征伙伴被忽略。 最后，我们专注于中子物质并计算了状态方程和声速。 结果与其他计算以及中子星观测的近期贝叶斯分析进行了对比。 显示英文摘要

摘要： We consider isospin-asymmetric matter in the parity-doublet model within an extended mean-field calculation, increasing continuously the neutron excess all the way to pure neutron matter. We compute the liquid-gas and the chiral phase transitions occurring at zero to moderate temperatures, but put special emphasis on the phase structure of matter at zero temperature and large baryon densities. The calculation of the free energy involves the solution of gap equations. This is achieved by transforming these gap equations into ordinary differential equations that control the flow with increasing baryon density of various physical quantities: the isoscalar condensate, the densities of protons and neutrons, as well as those of their respective chiral partners. In this formulation, the initial conditions for the differential equations determine the entire phase structure. It is further demonstrated that the threshold for the onset of the population of the chiral partners is exclusively determined by the fermionic parameters, most notably by the chiral-invariant mass of the nucleon. We underline the role of a parity symmetry energy in driving the equilibration of the nucleons and their parity partners across the chiral transition. We provide a detailed analysis of the changes in the matter properties as one varies the neutron excess, including a special discussion of the chiral limit, and we compare systematically the parity-doublet model to its corresponding singlet model, where the chiral partner of the nucleon is neglected. Finally, we focus on neutron matter and compute the equation of state and the speed of sound. The results are confronted to those of other calculations as well as to recent Bayesian analyses of neutron-star observations.