ORDER, CHAOS AND NUCLEAR DYNAMICS

Abstract
The purpose of the talk was to point out the relation between recent developments in nuclear dynamics and theories dealing with the transition from order to chaos in general. The leading idea can be stated very simply : a) when the nucleonic motions in the mean nuclear field are ordered, then the nucleus as a whole is expected to behave like an elastic solid, b) when the nucleonic motions are chaotic, the nucleus should behave like a very viscous fluid, dominated by the so-called one-body dissipation, c) when the nucleonic motions are intermediate, the nucleus should exhibit the properties of a visco-elastic material. Thus, in order to understand the dynamical evolutions of nuclear systems, such as take place in nuclear fission or nucleus-nucleus collisions, it is absolutely necessary to understand the degree of order in nucleonic motions and how this order may give place to chaos as the shape (and temperature) of a nuclear system changes in time. Examples illustrating these ideas were discussed, including giant quadrupole resonances, nuclear fission, the dynamical hindrance to compound nucleus formation and the centrifugal solidification of the ¹⁵²Dy superdeformed nucleus.