On the axial $U(1)$ symmetry at finite temperature
On the axial $U(1)$ symmetry at finite temperature
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有限温度下的轴 $U(1)$ 对称性
DOI：
10.22323/1.251.0196
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
A. Tomiya
中科院分区：
文献类型：
--
作者：
Jlqcd collaboration Guido Cossu;H. Fukaya;S. Hashimoto;J. Noaki;A. Tomiya
利用Möbius畴壁狄拉克算子研究了有限温度下双味晶格QCD中的$U(1)_A$异常。我们在不同的物理体积（$L=$ 2—4 fm）和晶格间距上生成温度范围$(0.9, 1.2) T_c$的测量配置。我们测量了风味非单重标量（$\chi_\delta$）和伪标量（$\chi_\pi$）介子的磁化率差异。它们通过轴向$U(1)$变换相关联，如果尊重轴向$U(1)$对称，差异就会消失。我们确定了轴向$U(1)$对称破缺的来源，在有限温度下的最低特征模态，为可观测的$\chi_\pi - \chi_\delta$。然后，我们将Möbius域壁费米子配分函数重新加权为重叠狄拉克算子的配分函数，以完全恢复手性对称性。我们的数据显示，来自Möbius畴壁价夸克、DWF构型上的重叠价夸克和具有完全手性对称的重加权价夸克的结果存在显著差异。在恢复完全的手性对称后，我们得出结论，差异$\chi_\pi - \chi_\delta$显示了手性极限的抑制，这与标量介子通道中$U(1)_A$ at $T \gtrsim T_c$的有效恢复是兼容的。
We study the $U(1)_A$ anomaly in two-flavor lattice QCD at finite temperature with the M\"obius domain-wall Dirac operator. We generate gauge configurations in the temperature range $(0.9, 1.2) T_c$ on different physical volumes, $L=$ 2--4 fm, and lattice spacings. We measure the difference of the susceptibilities of the flavor non-singlet scalar ($\chi_\delta$) and pseudoscalar ($\chi_\pi$) mesons. They are related by an axial $U(1)$ transformation and the difference vanishes if the axial $U(1)$ symmetry is respected. We identify the source of axial $U(1)$ symmetry breaking at finite temperature in the lowest eigenmodes, for the observable $\chi_\pi - \chi_\delta$. We then reweight the M\"obius domain-wall fermion partition function to that of the overlap-Dirac operator to fully recover chiral symmetry. Our data show a significant discrepancy in the results coming from the M\"obius domain-wall valence quarks, the overlap valence quarks on our DWF configurations and the reweighted ones that have full chiral symmetry. After recovering full chiral symmetry we conclude that the difference $\chi_\pi - \chi_\delta$ shows a suppression in the chiral limit that is compatible with an effective restoration of $U(1)_A$ at $T \gtrsim T_c$ in the scalar meson channels.
QCD高温相UA(1)对称性破坏的微观起源
影响因子：
5
作者：
V. Dick;F. Karsch;E. Laermann;S. Mukherjee;S. Sharma
通讯作者：
S. Sharma