arXiv 1206.09012012-06hep-phhep-lat

热重介质中的强子物态方程与声速

Hadronic Equation of State and Speed of Sound in Thermal and Dense Medium

Abdel Nasser Tawfik, Hend Magdy

备注：: 19 pages, 6 figures with 13 eps graphs
发表信息：: Int. J. Mod. Phys. A 29 (2014) 1450152
DOI：: 10.1142/S0217751X14501528

摘要：

本文研究了质量为$\leq 2\,$ GeV的强子共振巨正则系综的状态方程$p(ε)$和声速平方$c_s^2$。这个大的合奏分为奇怪的和非奇怪的强子共振，并进一步pionic，玻色子和femionic部门。结果表明，π介子是低温下$c_s^2$和包括状态方程$p(ε)$在内的其它热力学量的主要贡献者.在高温下，主要贡献是由大质量强子共振增加的。声速的平方可以由压力对能量密度的导数$\partial p/\partial ε$或熵比热比$s/c_v$计算得出。它的结论是，这两个表达式的物理不一定是相同的。它们在低于和高于临界温度$T_c$时是可区分的。这种行为是在消失和有限的化学势。在高温下，这两个表达式变得非常接近彼此，并且它们都接近渐近值$1/3$。在HRG结果中，仅在低于$T_c$时有效，差异随着温度的升高而减小，并且在接近$T_c$时几乎消失。结果表明，HRG模型能很好地再现$\partial p/\partial ε$和$s/c_v$的晶格量子色动力学（QCD）结果，特别是在有限化学势下。鉴于此，与比热相关的能量波动和其他集体现象可能存在于HRG模型中。在固定温度下，发现$c_s^2$对化学势不敏感。

英文摘要：

The equation of state $p(ε)$ and speed of sound squared $c_s^2$ are studied in grand canonical ensemble of all hadron resonances having masses $\leq 2\,$GeV. This large ensemble is divided into strange and non-strange hadron resonances and furthermore to pionic, bosonic and femionic sectors. It is found that the pions represent the main contributors to $c_s^2$ and other thermodynamic quantities including the equation of state $p(ε)$ at low temperatures. At high temperatures, the main contributions are added in by the massive hadron resonances. The speed of sound squared can be calculated from the derivative of pressure with respect to the energy density, $\partial p/\partial ε$, or from the entropy-specific heat ratio, $s/c_v$. It is concluded that the physics of these two expressions is not necessarily identical. They are distinguishable below and above the critical temperature $T_c$. This behavior is observed at vanishing and finite chemical potential. At high temperatures, both expressions get very close to each other and both of them approach the asymptotic value, $1/3$. In the HRG results, which are only valid below $T_c$, the difference decreases with increasing the temperature and almost vanishes near $T_c$. It is concluded that the HRG model can very well reproduce the results of the lattice quantum chromodynamics (QCD) of $\partial p/\partial ε$ and $s/c_v$, especially at finite chemical potential. In light of this, energy fluctuations and other collective phenomena associated with the specific heat might be present in the HRG model. At fixed temperatures, it is found that $c_s^2$ is not sensitive to the chemical potential.

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