Integral Representations of Causal Commutators

Abstract

An integral representation is found for the matrix element, between given states, of the commutator of two field operators. The representation makes use of the information derivable from the local commutativity of the operators and from the mass spectrum of the fields. The representation was discovered by Jost and Lehmann and proved by them for the case of two fields of equal mass. It is here extended to the case of unequal masses.