Nonlinear dynamics of nuclear collective motion

The nucleus is an isolated finite many-body quantum system, in which the se lf-consistent mean-field is realized. The system reveals the characteristic facets of the surprising coexistence of "macroscopic" and "microscopic" ef fects in association with various "phase transitions". Contrary to the infi nite many-body systems at the macroscopic level in which the phase transiti on happens sharply, the nucleus as the finite quantum system requires for u s to develop a microscopic theory of analyzing the phase transition in term s of the individual quantal states on the basis of the nonlinear dynamics. The characteristic difficulties in developing the microscopic theory rest o n the following fact: Because of the finite self-bound system, in the nucle us, the single-particle modes of motion (more generally, non-collective deg rees of freedom) have to adjust their features self-consistently, in accord ance with the time-evolution of the mean-field associated with the large-am plitude collective motion. Keeping the strong self-consistency between the single-particle motion and the collective motion, one has to develop the mi croscopic theory which is capable of explaining appearance, persistency, tr ansfiguration and termination of the large-amplitude collective motion. We hope that such a challenge may provide us to explore "quantum mechanical th eory of nonlinear dynamics", and give a clue to explain the thermal feature in isolated systems, as a result of the reversible process without any sta tistical hypothesis. In this paper, the efforts so far made by us are revie wed, towards the microscopic theory of the nonlinear dynamics of nuclear co llective motion.