Singularities of current commutators on the light cone

Abstract

We consider the forward proton matrix element of the electromagnetic current commutator and express its singularities on the light cone in terms of the scaling functions. This relation between the light cone and the deep inelastic region implies a family of sum rules for the electroproduction structure functions and connects the equal time commutators with the scaling functions. In particular the operator part of the Schwinger term and the related divergences of the electromagnetic mass of the proton are expressed in terms of measurable quantities.