Simple Non-Linear Klein–Gordon Equations in Two Space Dimensions,with Long-Range Scattering

We establish that solutions, to the most simple non-linear Klein–Gordon (NLKG) equations in two space dimensions with mass resonance, exhibits long-range scattering phenomena. Modified wave operators and solutions are constructed for these equations. We also show that the modified wave operators can be chosen such that they linearize the non-linear representation of the Poincaré group defined by the NLKG.