An expression in quantum-field-theoretic language of the four-space formulation (FSF), especially the FSF group properties, is derived by generalizing Schwinger's formulation of Lagrangian quantum field theory (LQFT). The resulting theoretical framework includes a mass operator in addition to the energy-momentum and angular momentum operators. It also contains LQFT as a special case. Broad conclusions regarding conservation laws (of rest mass, energy-momentum, and angular momentum) are obtained from the general formalism. Many mathematical details concerning the FSF group and FSF transformations are presented.

• Received 12 December 1978

DOI:https://doi.org/10.1103/PhysRevD.20.3108