Techniques for quantizing currents in Lagrangian field theory are developed with the aid of Zimmermann's normal products. These methods greatly simplify the derivation of single-current generalized Ward identities and may be used to justify the heuristic use of formal arguments in discussing broken symmetries. Applications to the energy-momentum tensor in the $A^4$ model and to the current of broken orthogonal symmetry in a two-component scalar model are presented.

• Received 17 June 1971

DOI:https://doi.org/10.1103/PhysRevD.4.2281