Localization in discontinuous quantum systems

Classical and quantum properties of a discontinuous perturbed twist map are investigated. Different classical diffusive regimes, quasilinear and slow respectively, are observed. The regime of slow classical diffusion gives rise to two distinct quantal regimes, one marked by dynamical localization, the other by quasi-integrable localization due to classical Cantori. In both cases the resulting quantum stationary distributions are algebraically localized.