VALIDITY OF BASIC CONCEPTS IN NONLINEAR COOPERATIVE FOKKER-PLANCK MODELS

The stochastic amplification of a periodic signal in a truly nonlinear Fokker-Planck model, whose drift coefficient exhibits a functional de pendence on the distribution function, is analyzed numerically by mean s of a finite-difference method. Our aim is to check the validity of b asic concepts widely used in studying linear and/or undriven systems. A perturbation approach to numerically evaluate the generalized suscep tibility of the model by means of the linear response theory is tested and found to be adequate for weak driving fields. We also check the v alidity of the Floquet theory and the H theorem for which no extension to the case of truly nonlinear driven systems exists. The influence o f the functional nonlinearity on the typical stochastic resonance effe cts is pointed out.