# Tag Info

The Dirac operator, as we know it, is $D_\mu\gamma^\mu$ with $D$ as the gauge covariant derivative. Using the Fujikawa method of deriving the Adler-Bell-Jackiw or chiral anomaly, one finds that the anomaly of the chiral current is given by $$\partial_\mu \langle (j^5)^\mu\rangle = 2 \mathrm{i}A(x)$$ where  A(x) = \int \sum_n \psi_n^\dagger \gamma^5 ...