Abstract
The canonical formalism for nonlinear relativistic classical field theory is presented. It is shown that the solutions Φ (x) of the nonlinear equation (⧠+m
2) Φ (x) =λΦ3(x) as well as the asymptotic fields Φin(x) and Φout(x) are local relativistic fields with respect to Poisson brackets, with initial data as canonical variables. A convenient form for the generators of the Poincaré group is derived, and the properties of the scattering operator are discussed.