One-time equation for the scattering of a particle on a bound state in quantum field theory

It is shown how the one-time formulation of the relativistic many-body problem leads to a quasipotential equation for the scattering of two particles one of which is a bound state of two other particles. The effective potential of such an interaction canbe expressed in terms of the binary interaction quasipotentials and also a quasipotential that cannot be reduced to a binary one.