title: Topological approximation of the nonlinear Anderson model.
abstract: We study the phenomena of Anderson localization in the presence of nonlinear interaction on a lattice. A class of nonlinear Schrödinger models with arbitrary power nonlinearity is analyzed. We conceive the various regimes of behavior, depending on the topology of resonance overlap in phase space, ranging from a fully developed chaos involving Lévy flights to pseudochaotic dynamics at the onset of delocalization. It is demonstrated that the quadratic nonlinearity plays a dynamically very distinguished role in that it is the only type of power nonlinearity permitting an abrupt localization-delocalization transition with unlimited spreading already at the delocalization border. We describe this localization-delocalization transition as a percolation transition on the infinite Cayley tree (Bethe lattice). It is found in the vicinity of the criticality that the spreading of the wave field is subdiffusive in the limit t→+∞. The second moment of the associated probability distribution grows with time as a power law ∝ t^{α}, with the exponent α=1/3 exactly. Also we find for superquadratic nonlinearity that the analog pseudochaotic regime at the edge of chaos is self-controlling in that it has feedback on the topology of the structure on which the transport processes concentrate. Then the system automatically (without tuning of parameters) develops its percolation point. We classify this type of behavior in terms of self-organized criticality dynamics in Hilbert space. For subquadratic nonlinearities, the behavior is shown to be sensitive to the details of definition of the nonlinear term. A transport model is proposed based on modified nonlinearity, using the idea of "stripes" propagating the wave process to large distances. Theoretical investigations, presented here, are the basis for consistency analysis of the different localization-delocalization patterns in systems with many coupled degrees of freedom in association with the asymptotic properties of the transport.
authors.affiliation: ENEA National Laboratory, Centro Ricerche Frascati, I-00044 Frascati, Rome, Italy Space Research Institute, Russian Academy of Sciences, 117997 Moscow, Russia and Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Milovanov
authors.affiliation: Department of Physics and Solid State Institute, Technion, Haifa, 32000, Israel and Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Iomin
mesh_terms: D004058:Diffusion; D008962:Models, Theoretical; D009038:Motion; D017711:Nonlinear Dynamics