Theory of Interacting Fermi Systems - The objective of the project is to acquire a deeper understanding of electron-electron interactions and their manifestations in solids. One approach toward this goal will be the study of physical properties which have been found to exhibit unexpected anomalous behavior, e.g., phenomena which can be attributed to broken symmetries caused by electron-electron interactions. Specific topics proposed for study include the longitudinal Hall effect in K at very low temperatures, ultraviolet optical anomalies in alkali metals, two magnon exchange in antiferromagnetic superconductors, phonon anomalies (possibly related to spin density waves) in zinc, cadmium, and technetium, fractional crystallization in 'optical molasses', and perpendicular-field cyclotron-resonance transmission in simple metals. %%% The best-established model descriptions for the behavior of electrons in solids are based on a picture where electrons are nearly independent of each other. Although such a viewpoint is quite successful, there are nevertheless a large number of important phenomena which cannot be explained properly by this approach. When electron-electron interactions become important, new theoretical descriptions must be developed. This project is aimed at developing such descriptions for a range of phenomena which appear experimentally and appear to depend explicitly on electron-electron interactions.
