Browsing by Author "Skokos C"

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    Nonlinear waves in disordered chains: probing the limits of chaos and spreading.
    (AMER PHYSICAL SOC, 2011-07) Bodyfelt JD; Laptyeva TV; Skokos C; Krimer DO; Flach S
    We probe the limits of nonlinear wave spreading in disordered chains which are known to localize linear waves. We particularly extend recent studies on the regimes of strong and weak chaos during subdiffusive spreading of wave packets [Europhys. Lett. 91, 30001 (2010)] and consider strong disorder, which favors Anderson localization. We probe the limit of infinite disorder strength and study Fröhlich-Spencer-Wayne models. We find that the assumption of chaotic wave packet dynamics and its impact on spreading is in accord with all studied cases. Spreading appears to be asymptotic, without any observable slowing down. We also consider chains with spatially inhomogeneous nonlinearity, which give further support to our findings and conclusions.
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    The crossover from strong to weak chaos for nonlinear waves in disordered systems
    (EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY, 1/08/2010) Laptyeva TV; Bodyfelt JD; Krimer DO; Skokos C; Flach S
    We observe a crossover from strong to weak chaos in the spatiotemporal evolution of multiple-site excitations within disordered chains with cubic nonlinearity. Recent studies have shown that Anderson localization is destroyed, and the wave packet spreading is characterized by an asymptotic divergence of the second moment m2 in time (as t1/3), due to weak chaos. In the present paper, we observe the existence of a qualitatively new dynamical regime of strong chaos, in which the second moment spreads even faster (as t1/2), with a crossover to the asymptotic law of weak chaos at larger times. We analyze the pecularities of these spreading regimes and perform extensive numerical simulations over large times with ensemble averaging. A technique of local derivatives on logarithmic scales is developed in order to quantitatively visualize the slow crossover processes. Copyright © 2010 EPLA.