Anomalies via dimensional regularization

Anomalous Ward identities arise when the Lagrangian in 2l-dimensional space-time is not invariant under the symmetry transformation in question withl arbitrary. (The anomalous symmetry-breaking terms have associated a factor 2l–4 and disappear at the classical level in four dimensions.) In particular, the axial anomaly is connected with the chiral breaking due to the fermion kinetic energy and the canonical trace anomaly is a consequence of dilatation non-invariance of any interaction.