Dynamic Many-Body Correlations

The goal of microscopic quantum many-body theory is the quantitative prediction of properties of interacting many-particle systems from no other information than the underlying microscopic input: particle number, temperature, statistics, and an empirical many-body Hamiltonian that incorporates the state-of-the-art knowledge of the particle interactions. The past decades have seen enormous progress in that area in the sense that the ground state properties of the most strongly interacting quantum fluids, i.e. the helium liquids, can be predicted with high accuracy. The situation is much less satisfactory for dynamic properties; the goal of the proposed work is to change this once and for all and to bring, at least for the case of Bose Fluids, the theoretical understanding of the dynamics of the systems to the same quantitative level that has been reached some time ago for the static ground state. Our work will have both analytic and numerical components. The method of choice is a generalization of the theory of correlated wave functions which has been most successful in describing ground state properties. In dynamic situations, all many-body correlations must be considered to be time dependent. The theory can actually be executed with no more approximations than those that were made for the ground state theory. We will examine the predictions of the dynamic correlated wave functions and compare with both experiments and analytically known ground state quantities that are related to the dynamics through sum rules and limits. Executing the same theory for fermions will be significantly more difficult, but also significantly more rewarding. We will make the point that neutron scattering data on mono-layers of 3 He are manifestly contradictory to \common wisdom" theoretical descriptions, and will argue that the approach chosen by us has the potential of providing an understanding of those experiments.

Die unter dem Projekt-Titel Dynamische Vielteilchen-Korrelationen durchgeführten Arbeiten waren ausgesprochen erfolgreich. Wir waren in der Lage, Beiträge zu aktuellen Fragen der Vielteilchen-Physik zu leisten, bei denen quantitative Methoden, welche in der Lage sind, auch stark wechselwirkenden Systemen zu behandeln, unerlässlich sind. Ein Erfolg unserer Strategie ist die Publikation eines unserer wesentlichen Resultate in Nature. Wir betonen, dass wir mit den theoretischen Entwicklungen begonnen haben bevor Experimente durchgeführt wurden, einfach weil wir davon überzeugt waren, die relevante Physik richtig zu beschreiben. Gegen Ende der Projektarbeit waren wir in der Lage, uns auch mit anderen aktuellen Problemen wie z. B. dem Problem der supersolids und kalten Gasen zu beschäftigen.