Summation of the Dominating Diagrams in Many-body Perturbation Theory

Abstract

In this paper we present a description of an approach within many-body perturbation theory, which takes into account the infinite series of diagrams that describe screening and the interaction between the excited-core electron and the hole. We also present an extension to this theory that allows us to describe the interaction of a positron with an atom. To do this the infinite series of diagrams that describes virtual positronium formation is taken into account. Some results of these calculations are presented.