Chaoticity in vibrating nuclear billiards.

We study the motion of classical particles con ned in a two-dimensional "nuclear" billiard whose walls undergo periodic shape oscillations according to a xed multipolarity. The presence of a coupling term in the single particle Hamiltonian between the particle motion and the collective coordinate generates a fully selfconsistent dynamics. We consider in particular monopole oscillations and demonstrate that self-consistency is essential in order to induce chaotic single-particle motion. We also discuss the dissipative behaviour of the wall motion and its relation with the order-to-chaos transition in the dynamics of the microscopic degrees of freedom. Analogous considerations can be extended to higher multipolarities. Pacs: 24.60.Lz, 21.10.Re The question about the origin of dissipation of collective motion in nite Fermi systems has been widely and deeply investigated [1], but its solution is still an open problem. One generally considers oneand two-body processes as the main mechanisms which could explain this phenomenon, though their mutual balance is currently a question