Coherence and Chaotic Resonances

Abstract

Real systems are subjected to certain amount of unavoidable internal or external random perturbations, usually termed as noise. The presence of noise is not only unavoidable in electrical and electronic devices, but it can significantly affect their performance. As pointed out in the beginning of Chap. 2, a variety of phenomena can be induced by the presence of noise. An oscillating system in which noise is significant and is the source of its oscillatory dynamics, then it is generally called an stochastic oscillator. A mathematical model of such a system in the absence of noise and external periodic force does not exhibit any kind of oscillatory motion. A stochastic oscillator can be monostable, multistable or excitable. In certain cases the effect of noise in a stochastic oscillator is nontrivial. That is, the increase of noise intensity need not always increase the irregularity of the response. An appropriate weak noise can give rise to a maximum coherence similar to the stochastic resonance but in the absence of any external periodic force.