The Graphical Unitary Group Approach and Its Application to Direct Configuration Interaction Calculations

Abstract

In his contribution to this volume,1 Paldus provides an excellent introduction and overview for the unitary group approach (UGA) to the many-electron correlation problem. In an earlier review2 he has given a comprehensive account of the historical and mathematical background of this approach and has provided a rigorous presentation of many of its aspects. Many additional facets of UGA and its relationship to other approaches have been explored in detail in his other publications on this subject. 3–12 In the present contribution we shall rely extensively on these papers, and particularly on the reviews in References 1 and 2, to provide the background and mathematical rigor, and shall focus primarily on a largely intuitive presentation of a particular form and mode of application of UGA13–27 which has come to be known as the graphical unitary group approach (GUGA).15–23