Unitary Group Approach to Many-Electron Correlation Problem

Abstract

The main purpose of this article is to present a brief outline of the unitary group approach to the many-electron correlation problem. its underlying principles. development and present achievements. as well as its relationship to other approaches to the problem of spin adaptation and Hamiltonian matrix evaluation. Thus. a founda- tion will be laid for the subsequent articles in these proceedings which address these problems from different viewpoints and in much greater detail. and also deal with and suggest solutions to the various facets of this and related topics. The space avail- able here is clearly inadequate to cover all these aspects at any length. Conse- quently. we will restrict ourselves to a brief outline. giving appropriate references and. wherever possible. illustrating the underlying concepts via simple examples and physical intuition rather than attempting to develop a mathematically rigorous general theory.