Towards satisfactory scattering amplitudes for dual fermions

The authors find the modified Lorentz invariant propagator which, when used on Neveu-Schwarz meson lines joining fermion lines, guarantees the coupling of just the ghost-free transverse spectrum of meson states. The modification is necessary to take account of the new form of reflected Ward identity valid for such lines. Thus they can write down dual amplitudes for processes involving four external fermions which possess a high degree of inner consistency, no-ghost theorems and Lorentz invariance, but they have not yet been able to evaluate them. (13 refs).