Detection of Arnold diffusion in Hamiltonian systems

We detect diffusion along resonances in a quasi-integrable system at small values of the perturbing parameter. The diffusion coefficient goes to zero, as the perturbation parameter goes to zero, faster than a power law, typical of Chirikov diffusion, and is compatible with an exponential law expected in the Nekhoroshev theorem. (C) 2003 Elsevier B.V. All rights reserved.