TITLE: Splitting of separatrices for (fast) quasiperiodic forcing AUTHOR: Amadeu Delshams(1), Vassili Gelfreich(2), Angel Jorba(1), Tere M. Seara(1). (1) Dept. de Matematica Aplicada I (ETSEIB), Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain). E-mails: amadeu@ma1.upc.es, angel@tere.upc.es, tere@ma1.upc.es (2) Departament de Matematica Aplicada i Analisi, Universitat de Barcelona, Gran Via 585, 08007 Barcelona (Spain) and Chair of Applied Mathematics, St. Petesburg Academy of Aerospace Instrumentation 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.