Constraints on hadronic current operators in relativistic quantum-mechanical models

Abstract

The conditions of current conservation and Poincaré invariance are reduced to a set of four equations that must be satisfied by the charge density at the origin. These equations require that the charge density has nonvanishing many-body (exchange current) corrections for systems of interacting particles in the one-photon exchange approximation. A large class of currents with acceptable many-body corrections are exhibited. The problem of how to construct minimal many-body corrections to one-body current operators that restore current conservation and Poincaré invariance is discussed.