2007/10/13 by G. Kopidakis, S. Komineas, S. Flach +1
Physics and Astronomy · #cond-mat.dis-nn
paper · pdf · doi:10.1103/physrevlett.100.084103
published as Phys. Rev. Lett. 100, 084103 (2008)
arxiv created 2007/10/13 · arxiv updated 2009/12/01
We study the spreading of an initially localized wavepacket in two nonlinear chains (discrete nonlinear Schroedinger and quartic Klein-Gordon) with disorder. Previous studies suggest that there are many initial conditions such that the second moment of the norm and energy density distributions diverge as a function of time. We find that the participation number of a wavepacket does not diverge simultaneously. We prove this result analytically for norm-conserving models and strong enough nonlinearity. After long times the dynamical state consists of a distribution of nondecaying yet interacting normal modes. The Fourier spectrum shows quasiperiodic dynamics. Assuming this result holds for any initially localized wavepacket, a limit profile for the norm/energy distribution with infinite second moment should exist in all cases which rules out the possibility of slow energy diffusion (subdiffusion). This limit profile could be a quasiperiodic solution (KAM torus).