论文标题
QCD手性和轴向破裂的新方面
New aspect of chiral and axial breaking in QCD
论文作者
论文摘要
仅仅是因为量子轴向异常的存在，违反QCD中$ u（1）$轴向对称性比手性$ su（2）$ breaking更为严格。如果将QCD量规耦合发送至零，则$ u（1）$轴向断裂的强度与手性$ su（2）$ breaking的强度相吻合，我们简而言之，我们将轴向手续的巧合。这种巧合是微不足道的，因为QCD然后成为一种非相互作用的理论。 Actually, there exists another limit in the QCD parameter space, where an axial-chiral coincidence occurs even with nonzero QCD gauge coupling, that can be dubbed a nontrivial coincidence: it is the case with the massive light quarks $(m_l\neq 0)$ and the massless strange quark ($m_s=0$), due to the flavor-singlet nature of the topological susceptibility.这种巧合是强大的，并与异常的手性沃德 - 塔卡哈西身份绑在一起，即使在HOT QCD上也是可操作的。这意味着手性$ su（2）$对称是在高温下与$ u（1）$轴向对称性同时恢复的。这种同时修复独立于$ m_l（\ neq 0）$，因此无论手学相变的顺序如何。在本文中，我们讨论了如何通过使用$ U（1）$ axial Anomaly贡献的Nambu-Jona-Lasinio模型来从非平凡的手性 - 轴巧合限制发展。结果表明，在高温下，手性$ su（2）$对称性的修复和$ u（1）$ u（1）$ a轴向对称性是两个光夸克和奇异夸克的足够大电流质量，这是由拓扑易感性的重大干扰引起的。因此，由控制拓扑敏感性的奇怪夸克质量监测的非平凡巧合的偏差提供了一种理解手性$ su（2）$（2）$和$ u（1）$ a axial axial breaking qcd中的新方法。
Violation of the $U(1)$ axial symmetry in QCD is stricter than the chiral $SU(2)$ breaking, simply because of the presence of the quantum axial anomaly. If the QCD gauge coupling is sent to zero, the strength of the $U(1)$ axial breaking coincides with that of the chiral $SU(2)$ breaking, which we shall in short call an axial-chiral coincidence. This coincidence is trivial since QCD then becomes a non-interacting theory. Actually, there exists another limit in the QCD parameter space, where an axial-chiral coincidence occurs even with nonzero QCD gauge coupling, that can be dubbed a nontrivial coincidence: it is the case with the massive light quarks $(m_l\neq 0)$ and the massless strange quark ($m_s=0$), due to the flavor-singlet nature of the topological susceptibility. This coincidence is robust and tied to the anomalous chiral Ward-Takahashi identity, which is operative even at hot QCD. This implies that the chiral $SU(2)$ symmetry is restored simultaneously with the $U(1)$ axial symmetry at high temperatures. This simultaneous restoration is independent of $m_l (\neq 0)$, hence is irrespective to the order of the chiral phase transition. In this paper, we discuss how the real-life QCD can be evolved from the nontrivial chiral-axial coincidence limit, by working on a Nambu-Jona-Lasinio model with the $U(1)$ axial anomaly contribution properly incorporated. It is shown that at high temperatures the large differences between the restorations of the chiral $SU(2)$ symmetry and the $U(1)$ axial symmetry for two light quarks and a sufficiently large current mass for the strange quark is induced by a significant interference of the topological susceptibility. Thus the deviation from the nontrivial coincidence, which is monitored by the strange quark mass controlling the topological susceptibility, provides a new way of understanding the chiral $SU(2)$ and $U(1)$ axial breaking in QCD.
