Strong interaction effects in electroweak corrections

We have seen in the previous chapter that the calculation of the two-loop electroweak corrections to the muon anomalous magnetic moment involves correlators of an axial current with two vector currents. Studies of such correlators in late sixties lead to the discovery of the anomaly of the axial current [1, 2]; implications of this phenomenon include computation of the decay amplitude for π₀ → γγ, 't Hooft consistency condition [3], solution of the U(1) problem etc. In case of the muon magnetic moment, such "anomalous" current correlators are important as well.