A soft mode in a finite Fermi-system: anharmonic effects near the instability point

Abstract

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.

Comments: 11 pages, 2 figures