Cumulant approach and coupled-cluster method for many-particle systems

• Published in: Molecular physics Vol. 94; no. 1; pp. 217 - 223
• Main Authors: BECKER, KLAUS W., VOJTA, MATTHIAS
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 01.05.1998
• ISSN: 0026-8976; 1362-3028
• DOI: 10.1080/002689798168501

Cumulants represent a natural language for expressing macroscopic properties of many-body systems. The most important property of cumulants is that of size consistency, i.e. a cumulant expression for an extensive variable scales with the size of the system, independent of possible further approximations used in the evaluation procedure. Cumulants can be considered as a generalization of linked diagrams known from diagrammatic technique of many-body theory. In this paper we outline a recently introduced method based on cumulants in order to derive expressions for zero-temperature properties of many-particle systems, i.e. the ground-state energy, static expectation values and dynamical correlation functions. This cumulant formalism allows one to describe weakly and strongly correlated systems along the same lines. We show that the coupled-cluster method known from quantum chemistry can be derived from our cumulant approach. Finally, we demonstrate the usefulness of the cumulant method by applying it to examples from solid-state physics and quantum chemistry.