Speed of Sound in Asymmetric Quark Matter

非对称夸克物质中的声速

The speed of sound in quark matter is an important physical quantity for studying the properties and the spacetime evolution of quark-gluon plasma(QGP).The behavior of the speed of sound with respect to temperature and density can reveal to some extent the equation of state and the phase structure of QGP.Building upon the previous studies on the speed of sound in symmetric quark matter,the formulae for calculating the speed of sound in asymmetric quark matter in the temperature-density space are further derived.The PNJL model is then used to calculate the dependence of the speed of sound on isospin asymmetry.Furthermore,the relationship between the magnitude of the speed of sound and the QCD phase structure is discussed,and the regions where the acoustic equation fails are indicated under different physical conditions.It is found that the boundary of vanishing sound speed in asymmetric quark matter is smaller than that in symmetric quark matter,meaning that the range where the acoustic wave equation fails in asymmetric quark matter is smaller than that in symmetric quark matter.The results also indicate that in most of the stable phase,the speed of sound in asymmetric quark matter is slightly larger than that in symmetric quark matter.

夸克物质中的声速是研究夸克-胶子等离子体(QGP)的性质和时空演化的一个重要物理量,声速随温度和密度的变化行为在一定程度上能够揭示QGP的物态方程和相结构。在之前研究对称夸克物质中声速的基础上,本工作进一步推导了在温度和密度空间计算非对称夸克物质声速的公式,并利用PNJL模型计算了夸克物质中的声速对同位旋不对称参数的依赖,讨论了声速的大小与QCD相结构的关系,指出了不同物理条件下声波方程失效的范围。结果表明,非对称夸克物质中声速平方小于零的区域小于对称夸克物质,这意味着非对称夸克物质中声波方程失效的范围小于对称夸克物质。计算还表明,在稳定相的大部分区域,非对称夸克物质中的声速略大于对称夸克物质的声速。