  In order to understand the origin of one-body dissipation in nuclei, we
analyze the behavior of a gas of classical particles moving in a
two-dimensional cavity with nuclear dimensions. This "nuclear" billiard has
multipole-deformed walls which undergo periodic shape oscillations. We
demonstrate that a single particle Hamiltonian containing coupling terms
between the particles' motion and the collective coordinate induces a chaotic
dynamics for any multipolarity, independently on the geometry of the billiard.
If the coupling terms are switched off the "wall formula" predictions are
recovered. We discuss the dissipative behavior of the wall motion and its
relation with the order-to-chaos transition in the dynamics of the microscopic
degrees of freedom.
