Table of contents

Stochastic resonance (SR) provides a glaring example of a noise-induced transition in a nonlinear system driven by an information signal and noise simultaneously. In the regime of SR some characteristics of the information signal (amplification factor, signal-to-noise ratio, the degrees of coherence and of order, etc.) at the output of the system are significantly improved at a certain optimal noise level. SR is realized only in nonlinear systems for which a noise-intensity-controlled characteristic time becomes available. In the present review the physical mechanism and methods of theoretical description of SR are briefly discussed. SR features determined by the structure of the information signal, noise statistics and properties of particular systems with SR are studied. A nontrivial phenomenon of stochastic synchronization defined as locking of the instantaneous phase and switching frequency of a bistable system by external periodic force is analyzed in detail. Stochastic synchronization is explored in single and coupled bistable oscillators, including ensembles. The effects of SR and stochastic synchronization of ensembles of stochastic resonators are studied both with and without coupling between the elements. SR is considered in dynamical and nondynamical (threshold) systems. The SR effect is analyzed from the viewpoint of information and entropy characteristics of the signal, which determine the degree of order or self-organization in the system. Applications of the SR concept to explaining the results of a series of biological experiments are discussed.

The concept of stochastic resonance (SR) was introduced in 1981 in the study of ice-age periodicity in the northern hemisphere. To describe this phenomenon, a relaxation model — an overdamped bistable oscillator — is used. SR is caused by the simultaneous action of a periodic signal and noise and appears as a nonmonotone response to noise intensity variations. Since the subject of the study is actually the filter passband width as a function of noise intensity, 'stochastic filtering' (SF) seems to be a more appropriate term to describe the phenomenon. It is shown that when driven by a signal and noise, a low-attenuation bistable oscillator also displays ordinary SR when the signal frequency coincides with the effective noise-intensity-dependent frequency of the oscillator. Thus the possibility of the resonance being controlled by varying the noise intensity arises.