A relativistic Hamiltonian theory in the light-like case

Abstract

A version of a relativistic Hamiltonian theory is developed in which the four-momentum of the spurion lies on the light cone. A new point of this scheme is a specific regularisation by which the singularities accompanying each field theory in light-front variables are removed in all diagrams. The unitarity and causality conditions are analysed in detail. It is shown that the choice of regularisation is defined by the causality condition. In the framework of the scheme developed, a quasipotential-type equation for the two-particle scattering amplitude is obtained. Various forms of this equation and their relations with previous quasipotential equations are considered.