INFRARED DIVERGENCES IN THE KONDO PROBLEM

Using a slave boson formulation of the numerical RG we investigate the pseudo-particle spectral functions of the resonant level and Anderson impurity models subject to the constraint of no double occupancy. The spectral functions for the pseudo-fermions, rho(f)(omega), and slave- bosons, rho(b)(omega), show threshold behaviour \omega-E(0)\(-alpha f, b), where E(0) is the groundstate energy, and the exponents alpha(f,b) are related to the conduction electron phase-shift at the Fermi level . Vertex corrections to the local Greens function are singular at the threshold and play an important role in restoring the known Fermi liqu id behaviour of these models.