arXiv 2012.062312020-12-11hep-ph

QCD中手性和有效的$U(1)_{\rm A}$对称性恢复

Chiral and effective $U(1)_{\rm A}$ symmetry restoration in QCD

Jens Braun, Marc Leonhardt, Jan M. Pawlowski, Daniel Rosenblüh

备注：: 13 pages, 6 figures

摘要：

接近手征极限的QCD相变的性质和位置限制了具有非零密度物理π质量的QCD的相结构。在小的π介子质量，明确的$U(1)_{\rm A}$破缺，诱导的非平凡的拓扑密度，是非常重要的。它触发了特胡夫特相互作用，也表现在低动量尺度下四夸克相互作用的相互作用中。在目前的工作中，我们进行了Fierz完全分析的出现四夸克相互作用的QCD动力学在有限的温度下，在一个给定的t Hooft耦合在大动量尺度。后者的变化使我们能够测试我们的研究结果的鲁棒性。考虑到t Hooft耦合的拓扑运行效应，我们的分析表明，具有两个无质量味夸克的QCD手征跃迁属于普适类$O(4)$.

英文摘要：

The nature and location of the QCD phase transition close to the chiral limit restricts the phase structure of QCD with physical pion masses at non-vanishing density. At small pion masses, explicit $U(1)_{\rm A}$-breaking, as induced by a non-trivial topological density, is of eminent importance. It triggers the 't Hooft interactions and also manifests itself in the interplay of four-quark interactions at low momentum scales. In the present work, we perform a Fierz-complete analysis of the emergence of four-quark interactions from the QCD dynamics at finite temperature, subject to a given 't Hooft coupling at large momentum scales. The variation of the latter allows us to test the robustness of our findings. Taking an estimate of the effect of the topological running of the 't Hooft coupling into account, our analysis suggests that the chiral transition in QCD with two massless quark flavours falls into the $O(4)$ universality class.

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英文摘要：

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