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arXiv · 1611.00434

Intermittent many-body dynamics at equilibrium

C. Danieli·D. K. Campbell·S. Flach
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Abstract

The equilibrium value of an observable defines a manifold in the phase space of an ergodic and equipartitioned many-body system. A typical trajectory pierces that manifold infinitely often as time goes to infinity. We use these piercings to measure both the relaxation time of the lowest frequency eigenmode of the Fermi-Pasta-Ulam chain (FPU), as well as the fluctuations of the subsequent dynamics in equilibrium. The dynamics in equilibrium is characterized by a power-law distribution of excursion times far off equilibrium, with diverging variance. Long excursions arise from sticky dynamics close to q-breathers localized in normal mode space. Measuring the exponent allows to predict the transition into nonergodic dynamics. We generalize our method to Klein-Gordon lattices (KG) where the sticky dynamics is due to discrete breathers localized in real space.

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C. Danieli, D. K. Campbell, S. Flach. 2017-02-12. Intermittent many-body dynamics at equilibrium. https://doi.org/10.1103/physreve.95.060202

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