在强相互作用中不存在$CP$破坏
Absence of $CP$ violation in the strong interactions
摘要：
在一般真空角存在的情况下，推导出具有复质量的大质量费米子的关联函数。为此，我们首先在单瞬子背景下建立格林函数，然后对背景瞬子的组态求和。拓扑扇区的量子化是针对无限时空体积中有限欧几里德作用量的鞍点以及关于这些鞍点的涨落而进行的。因此，对于所得到的关联函数，我们在拓扑扇区求和之前取无限体积极限。相反的顺序限制，手征相位从质量项和从瞬子效应，然后对齐，这样，在没有额外的阶段，这些不会引起违反电荷宇称对称性的可观测量。这一结果证实了约束时的相关重合点，使用的指标定理，而不是瞬子演算。
英文摘要：
We derive correlation functions for massive fermions with a complex mass in the presence of a general vacuum angle. For this purpose, we first build the Green's functions in the one-instanton background and then sum over the configurations of background instantons. The quantization of topological sectors follows for saddle points of finite Euclidean action in an infinite spacetime volume and the fluctuations about these. For the resulting correlation functions, we therefore take the infinite-volume limit before summing over topological sectors. In contrast to the opposite order of limits, the chiral phases from the mass terms and from the instanton effects then are aligned so that, in absence of additional phases, these do not give rise to observables violating charge-parity symmetry. This result is confirmed when constraining the correlations at coincident points by using the index theorem instead of instanton calculus.
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