Numerical renormalization group calculations for the self-energy of the impurity Anderson model

Abstract

We present a new method to calculate directly the one-particle self-energy of\nan impurity Anderson model with Wilson's numerical Renormalization Group method\nby writing this quantity as the ratio of two correlation functions. This way of\ncalculating Sigma(z) turns out to be considerably more reliable and accurate\nthan via the impurity Green's function alone. We show results for the\nself-energy for the case of a constant coupling between impurity and conduction\nband (ImDelta = const) and the effective Delta(z) arising in the Dynamical Mean\nField Theory of the Hubbard model. Implications to the problem of the\nmetal-insulator transition in the Hubbard model are also discussed.\n