Derivation of interaction potentials from field theory

A general formulation is given for the derivation of relativistic equations and associated potentials describing the field-theoretical interaction of two or more particles using a recently developed functional, field-theoretical formalism. The latter allows an exact single-time treatment which makes possible a global (i.e., off-shell) definition of the potential as a certain set of ''connected'' contributions. The potential thus obtained is a nonlocal operator with a precisely defined energy dependence. Simple, illustrative applications to N-electron and N-nucleon systems are given, and the one-boson exchange and annihilation potentials for the nucleon-antinucleon system are calcualted. The one-boson annihilation contribution is shown to be quite important. Remarks concerning the applicability of the formalism as well as extension to non-Abelian gauge theories are presented