Stochastic resonance of elastic string motion

A model for the motion of an elastic string is studied numerically and analytically. An elastic string in two dimensions and restricted by two pinning centers is considered. We consider two stable configurations (positively or negatively curved) with pinned ends due to the action of a bistable potential. It is further assumed that the string is driven externally by periodic and white noisy forces. The noise enables the string to flip between the two configurations. The small temporally periodic force synchronizes these flippings and the phenomenon of stochastic resonance is observed. The signal-to-noise ratio (SNR) of the output is investigated and shows a maximum for a nonvanishing intensity of the applied noise. Its dependence on the stiffness of the string is studied. The peak of SNR versus the noise intensity D is found to be more pronounced and to be shifted to small values of D with an increase in the effective stiffness of a string. The calculation is extended to stochastic resonance of vortex motion in a type II superconductor. For vortices restricted by two pinning centers, the characteristic time scale tau (R) relevant to the vortex dynamics is shown to depend crucially on the effective vortex stiffness, with the time tau (R) being extremely small for flexible vortices. Therefore, the effects of noise color on the vortex dynamics should be taken into account in many practical situations. (C) 2001 American Institute of Physics.