Splitting of separatrices for (fast) quasiperiodic forcing

Abstract

We consider fast quasiperiodic perturbations of a pendulum with two frequencies $(1,\gamma)$, where $\gamma$ is the golden mean number. For small perturbations such that its Fourier coefficients (the ones associated to Fibonacci numbers), are separated from zero, it is announced that the invariant manifolds split, and the value of the splitting, that turns out to be exponentially small with respect to the perturbation parameter, is correctly predicted by the Melnikov function. An explicit example shows that the splitting can be of the order of some power of $\varepsilon$ if the function $m$ is not analytic. This makes a qualitative difference between periodic and quasiperiodic perturbations