Estimation of Spectra from Moments—Application to the Hubbard Model

Abstract

We discuss the approximate calculation of a Green's function and its spectral density from its low-order moments by the use of ratio-extrapolation techniques to estimate and factor off the dominant shape of the band edges. The techniques are illustrated, following Brinkman and Rice, on the problem of a single hole propagating in ferromagnetic, antiferromagnetic, and random electron-spin configurations in the atomic limit of the Hubbard model; the methods are, however, of wider applicability.