X-RAY-EDGE SINGULARITIES WITH NONCONSTANT DENSITY-OF-STATES - A RENORMALIZATION-GROUP APPROACH

We present the results of a calculation of the x-ray absorption and ph otoemission spectra of metals based on the Wilson renormalization grou p (RG) (Wilson and co-workers) using free-electron, Lorentzian, and se micircular density of states. The deviation from the asymptotic singul ar behavior is studied. This illustrative calculation introduces an al gorithm for obtaining a tridiagonalized (hopping) Hamiltonian from the logarithmically discretized conduction band. We provide a detailed de scription of the algorithm which renders the study of problems of impu rities in metals with nonconstant conduction electron density of state s using the RG method feasible.