Eikonal Scattering of Monopoles and Dyons in Dual QED
  The quantum field theory of electron-point magnetic monopole interactions and dyon-dyon interactions, based on the string-dependent ``nonlocal'' action of Dirac and Schwinger is developed. We demonstrate that a nonperturbative quantum field theoretic formulation can be constructed resulting in a string {\em independent} cross section for monopole-electron and dyon-dyon scattering. Such calculations can be done only by using nonperturbative approximations such as the eikonal and not by some mutilation of lowest-order perturbation theory. 
Leonard Gamberg and Kimball A. Milton