Soft Interaction of Heavy Fermions
  We discuss a formula for the sum of tree diagrams of $n$-bosons scattering from a heavy fermion. This formula can be considered as a generalization of the eikonal formula to include non-abelian vertices. It will be used to demonstrate the consistency of multi-meson-fermion scattering in the large-$N_c$ limit. 
C.S. Lam (McGill University)