There are currently two singularity-free universal expressions for the topological susceptibility in QCD, one based on the Yang–Mills gradient flow and the other on density-chain correlation functions. While the latter link the susceptibility to the anomalous chiral Ward identities, the gradient flow permits the emergence of the topological sectors in lattice QCD to be understood. Here the two expressions are shown to coincide in the continuum theory, for any number of quark flavours in the range where the theory is asymptotically free.

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关于手征异常和杨-米尔斯梯度流

QCD 中的拓扑磁化率目前有两种无奇点通用表达式，一种基于 Yang-Mills 梯度流，另一种基于密度链相关函数。虽然后者将敏感性与异常手性 Ward 恒等式联系起来，但梯度流允许理解晶格 QCD 中拓扑扇区的出现。在这里，这两个表达式在连续统理论中是一致的，对于理论渐近自由范围内的任意数量的夸克味。