In condensed matter systems there are a large number of degrees of freedom which interact strongly with each other. Many phemonena, however, can be understood on the basis of a small number of degrees of freedom interacting on a single scale not significantly larger than the atomic length scale. A self-consistent one- particle theory can adequately describe these phenomena. In contrast, there are many instances in which it is impossible to guess the qualitative behavior of the system from a theory based on a few degrees of freedom. The aim of the present proposal is to examine correlation effects in these strongly interacting systems. In particular, theoretical research will be conducted on novel correlations in quantum antiferromagnets, on magnetic correlations in high temperature cuprate superconductors, and on electronic correlation effects in newly discovered superconductors made by doping fullerine molecular solids with alkali atoms. %%% The theoretical research will focus on the physics of various materials which cannot be understood using conventional models and techniques. These materials include the copper-based high temperature superconductors, magnetic materials and the newly discovered superconducting materials based on the new form of carbon, Buckminsterfullerine. New theoretical techniques will be developed to understand these complex systems.
