On the augmented-space cluster coherent-potential approximation and its analytic properties

Abstract
The authors discuss the analytic properties of the configuration-averaged Green function obtained using the self-consistent cluster coherent-potential approximation, developed in the augmented-space formalism. It is shown that the iteration scheme for the self-energy is always convergent to a unique value, which is bounded and herglotz, provided one starts off with a bounded and herglotz guess. This ensures that one shall always get a unique, non-negative density of states at all energies.