Surmounting collectively oscillating bottlenecksD. Hennig1, L. Schimansky-Geier1 and P. Hänggi2
1 Institut für Physik, Humboldt-Universität zu Berlin - Newton Str. 15, D-12489 Berlin, Germany
2 Institut für Physik, Universität Augsburg - Universitätsstr. 1, D-86135 Augsburg, Germany
received 30 June 2008; accepted in final form 1 August 2008; published September 2008
published online 11 September 2008
We study the collective escape dynamics of a chain of coupled, weakly damped nonlinear oscillators from a metastable state over a barrier when driven by a thermal heat bath in combination with a weak, globally acting periodic perturbation. Optimal parameter choices are identified that lead to a drastic enhancement of escape rates as compared to a pure noise-assisted situation. We elucidate the speed-up of escape in the driven Langevin dynamics by showing that the time-periodic external field in combination with the thermal fluctuations triggers an instability mechanism of the stationary homogeneous lattice state of the system. Perturbations of the latter provided by incoherent thermal fluctuations grow because of a parametric resonance, leading to the formation of spatially localized modes (LMs). Remarkably, the LMs persist in spite of continuously impacting thermal noise. The average escape time assumes a distinct minimum by either tuning the coupling strength and/or the driving frequency. This weak ac-driven assisted escape in turn implies a giant speed of the activation rate of such thermally driven coupled nonlinear oscillator chains.
05.40.-a - Fluctuation phenomena, random processes, noise, and Brownian motion.
63.20.Pw - Localized modes.
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