The Langevin equation and a more general approach to internal noise in nonlinear networks

In this paper, the failure of the well known generalized Langevin approach for the description of internal noise in nonlinear electrical networks is discussed. Using the equivalence between Langevin and Fokker-Plank equations, the results of Stratonovich´s systematic generalization of the linear theory of thermal noise are applied to a nonlinear RC network. (The authors have applied Stratonovich´s theory to larger classes of networks elsewhere.) This generalization makes extensive use of statistical thermodynamics, which is the fundamental input to the linear theory of thermal noise. Although the frequently used generalized Langevin approaches are, strictly speaking, incorrect, they appear to be a good approximations of a more general, correct description, which is based on first principles