Effects of Random Interactions in a Finite Fermi System

A.I. Vdovin, Daniel S. Kosov, W. Nawrocka

Vladimir Zelevinsky, Alexander Volya

We consider a finite Fermi-system where the residual interactions create a soft mode of the excitation spectrum. Because of the large vibrational amplitude, the standard random phase approximation does not work in this situation. We develop a regular method for constructing the anharmonic potential and illustrate the application of the formalism by a simple model.

Vladimir Zelevinsky, Alexander Volya

Ph. Nozières, Daniel W. Hone, M. E. Rose

Vladimir Zelevinsky, Alexander Volya

Numerical simulations show that the ground state spin of a finite many-body system with random but rotationally invariant interactions is predominantly zero. This means that it is not sufficient to explain the zero ground state spin of even-even nuclei only by pairing correlations. Simple explanations based on a statistical multiplicity, width of the level density, effective pairing, formation of condensates etc. do not work. We suggest statistical theory based on the effective mean field and geometric chaoticity of angular momentum coupling of individual particles. The results show a significant role of symmetry arguments in finite systems.

V. V. Flambaum, Felix M. Izrailev, Giulio Casati

The model of Fermi particles with random two-body interaction is investigated. This model allows one to study the origin and accuracy of statistical laws in few-body systems, the role of interaction and chaos in thermalization, the Fermi-Dirac distribution for quasiparticles with spreading widths, matrix elements of external fields, and enhancement of weak perturbation in chaotic compound states. \textcopyright{} 1996 The American Physical Society.