The relationship between various methods of solution of the Lippmann-Schwinger equation

The generalized Schwinger variational principle is shown to be equivalent to one of the three versions of the Rayski method. In the case of a spherically symmetric potential the Kohn-type variational principle is introduced and the relationship between methods mentioned above is found. Another version of the Rayski method is connected to a minimum variational principle and yields a convergent process for computing the exact solution of the Lippmann-Schwinger equation for the short-range potentials. (orig.)