On the existence of solutions to S matrix models
J. V. Greenman · Journal of Mathematical Physics · 1974
We analyze the charged scalar Low equation and show that, in this case at least, the breakdown of the standard fixed point theorems occurs because of their inherent weakness rather than through some topological change in the structure of the family of solutions. We also show that unless we reformulate the equation the Schauder principle only handles the basic solution, that solution without CDD poles. We discuss methods, alternative to the N/D method, to handle the other solutions.