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arXiv 1408.1189hep-ph
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QCD $θ$ -从手性极限到淬灭极限的真空

QCD $θ$-vacua from the chiral limit to the quenched limit

Kazuya Mameda

摘要:

我们利用Di-Vecchia-Veneziano模型研究了QCD真空结构对$θ$角和夸克质量的依赖性。虽然Di-Vecchia-Veneziano模型是一个手征有效模型,但它包含了纯杨-米尔斯理论的拓扑性质。结果表明,在这个模型中,所有$θ$的基态能量是夸克质量的连续函数,从手征极限到淬火极限,甚至包括在$θ= π$的一级相变。基于这个有效模型,我们讨论了(i)基态如何依赖于夸克质量,和(ii)为什么在$θ= π$相变存在于手征和淬火极限。为了分析夸克质量与$θ$ -真空的关系,我们计算了手征凝聚作为夸克质量的函数。同时,考虑到QCD $θ$ -真空中包含的固有亚稳态的存在,我们也对$θ= π$在手征极限和淬灭极限下的相变给出了统一的理解.

英文摘要:

We investigate the dependence of the QCD vacuum structure on the $θ$-angle and quark mass, using the Di-Vecchia--Veneziano model. Although the Di-Vecchia--Veneziano model is a chiral effective model, it contains the topological properties of the pure Yang--Mills theory. It is shown that within this model, the ground state energies for all $θ$ are continuous functions of quark mass from the chiral limit to the quenched limit, even including the first order phase transition at $θ= π$. Based on this effective model, we discuss (i) how the ground state depends on quark mass, and (ii) why the phase transition at $θ= π$ is present both in the chiral and quenched limit. In order to analyze the relation between quark mass and the $θ$-vacua, we calculate the chiral condensate as a function of quark mass. Also, considering the presence of the innate metastable states included in the QCD $θ$-vacuum, we also give a unified understanding of the phase transitions at $θ= π$ in the chiral and quenched limit.

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