Manifest covariance and the assumption that the equal-time commutators (ETC) of currents and spatial components of fields are no more singular than delta functions are shown to imply the cancellation of Schwinger and seagull terms in the divergence of the scattering amplitude. Slightly stronger assumptions about the field-current ETC used in previous work are shown to imply the more specific Schwinger-seagull relations found there, without the need of divergence conditions. The technique used is generally applicable to the study of the relation of Schwinger and seagull terms. The role of divergence conditions in previous work is discussed.

• Received 14 February 1967

DOI:https://doi.org/10.1103/PhysRev.158.1444