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arXiv 0909.5122hep-lathep-ph
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（2+1）味QCD的磁状态方程

On the magnetic equation of state in (2+1)-flavor QCD

S. Ejiri, F. Karsch, E. Laermann, C. Miao, S. Mukherjee, P. Petreczky, C. Schmidt, W. Soeldner, W. Unger

备注：
18 pages, 18 EPS-files
发表信息：
Phys.Rev.D80:094505,2009
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摘要：

首次研究了（2+1）味QCD的手征相变附近的临界行为。我们分析了具有两个简并轻夸克质量和一个奇异夸克的QCD中手征凝聚体的夸克质量和体积依赖性以及手征凝聚度。奇异夸克的质量（m_s）被选择为接近其物理值;两个简并轻夸克的质量（m_l）在1/80 \le m_l/m_s \le 2/5的宽范围内变化，其中最小的轻夸克质量值对应于大约75 MeV的赝标量戈德斯通质量。所有的计算进行交错费米子的晶格上的时间范围Nt=4。我们证明了在手征极限下数值结果与O（N）标度是一致的。我们发现在物理轻夸克质量值m_l/m_s \simeq 1/20的区域内，手征凝聚体的温度和夸克质量依赖性已经被编码在手征序参量标度函数（磁状态方程）中的QCD普适性质所支配。我们还提供了在有限温度下Goldstone模的热涨落对手征凝聚体的影响的证据。在低于但接近夸克质量消失时手征相变的温度下，这导致了轻夸克手征凝聚体对轻夸克质量平方根的特征依赖性。

英文摘要：

A first study of critical behavior in the vicinity of the chiral phase transition of (2+1)-flavor QCD is presented. We analyze the quark mass and volume dependence of the chiral condensate and chiral susceptibilities in QCD with two degenerate light quark masses and a strange quark. The strange quark mass (m_s) is chosen close to its physical value; the two degenerate light quark masses (m_l) are varied in a wide range 1/80 \le m_l/m_s \le 2/5, where the smallest light quark mass value corresponds to a pseudo-scalar Goldstone mass of about 75 MeV. All calculations are performed with staggered fermions on lattices with temporal extent Nt=4. We show that numerical results are consistent with O(N) scaling in the chiral limit. We find that in the region of physical light quark mass values, m_l/m_s \simeq 1/20, the temperature and quark mass dependence of the chiral condensate is already dominated by universal properties of QCD that are encoded in the scaling function for the chiral order parameter, the magnetic equation of state. We also provide evidence for the influence of thermal fluctuations of Goldstone modes on the chiral condensate at finite temperature. At temperatures below, but close to the chiral phase transition at vanishing quark mass, this leads to a characteristic dependence of the light quark chiral condensate on the square root of the light quark mass.

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