Strong and Weak Chaos in Weakly Nonintegrable Many-Body Hamiltonian Systems |
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Authors: | M Mulansky K Ahnert A Pikovsky D L Shepelyansky |
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Institution: | 1.Department of Physics and Astronomy,Potsdam University,Potsdam-Golm,Germany;2.Laboratoire de Physique Théorique du CNRS (IRSAMC), UPS,Université de Toulouse,Toulouse,France |
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Abstract: | We study properties of chaos in generic one-dimensional nonlinear Hamiltonian lattices comprised of weakly coupled nonlinear
oscillators by numerical simulations of continuous-time systems and symplectic maps. For small coupling, the measure of chaos
is found to be proportional to the coupling strength and lattice length, with the typical maximal Lyapunov exponent being
proportional to the square root of coupling. This strong chaos appears as a result of triplet resonances between nearby modes.
In addition to strong chaos we observe a weakly chaotic component having much smaller Lyapunov exponent, the measure of which
drops approximately as a square of the coupling strength down to smallest couplings we were able to reach. We argue that this
weak chaos is linked to the regime of fast Arnold diffusion discussed by Chirikov and Vecheslavov. In disordered lattices
of large size we find a subdiffusive spreading of initially localized wave packets over larger and larger number of modes.
The relations between the exponent of this spreading and the exponent in the dependence of the fast Arnold diffusion on coupling
strength are analyzed. We also trace parallels between the slow spreading of chaos and deterministic rheology. |
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