Combined variable-phase-off-shell scattering theory
We develop a first order linear differential equation for the fully off-shell scattering amplitude in terms of the cut-off radius of the local two-body interaction. The on- and half-off-shell equation of Calogero and of Sobel are derived as special cases. The input of our equation involves interpolating half off-shellT matrices parametrized by well known phase and quasiphase functions.