2007/05/07 by S. Flach, A. Ponno · 2 citations
Physics and Astronomy · #nlin.PS #nlin.CD
paper · pdf · doi:10.1016/j.physd.2007.11.017
14 pages, 4 figures
arxiv created 2007/05/07 · arxiv updated 2009/12/01
Fermi, Pasta and Ulam observed, that the excitation of a low frequency normal mode in a nonlinear acoustic chain leads to localization in normal mode space on large time scales. Fast equipartition (and thus complete delocalization) in the Fermi-Pasta-Ulam chain is restored if relevant intensive control parameters exceed certain threshold values. We compare recent results on periodic orbits (in the localization regime) and resonant normal forms (in a weak delocalization regime), and relate them to various resonance overlap criteria. We show that the approaches quantitatively agree in their estimate of the localization-delocalization threshold. A key ingredient for this transition are resonances of overtones.