Diffusion approximation for noise-induced evolution of first integrals in multifrequency systems

We consider fast oscillating perturbations of dynamical systems in regions where one can introduce action-angle type coordinates. In an appropriate time scale, a diffusion approximation of the first-integrals evolution is described under the assumption that the set of resonance tori is small enough. If the action-angle coordinates can be introduced just piece-wise , the limiting diffusion process should be considered on an open book space. Such a process can be described by differential operators, one on each page, supplemented by some gluing conditions on the binding of the open book.

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