on Meson-Nucleon Physics and the Structure of the Nucleon

Poincare ́ invariant instant form model for the pion-nucleon system has been constructed, which describes the coupling between single-baryon and meson-baryon channels. The elastic scattering amplitudes are obtained from three-dimensional Lippmann-Schwinger equations. The S-matrix elements for the various processes transform properly under inhomogeneous Lorentz transformations and moreover are gauge invariant. The mass-operator inter-actions that describe the processes µB → µ́B ́ , where B and B ́ are baryons and µ is a meson, have been derived. The interactions are assumed to be separable.