THE EFFECT OF RECOIL ON EDGE SINGULARITIES

A transient local perturbation gives rise to infrared edge singulariti es. These singularities are shown to disappear if the scatterer is fre e to diffuse to infinity, as long as the dimension exceeds 1. When d = 1, or in the presence of localization when d > 1, the characteristic exponents are reduced by recoil, by a factor that involves an angular average over the Fermi surface.