A Nekhoroshev theorem for some perturbations of the Benjamin-Ono equation with initial data close to finite gap tori

Abstract

We consider a perturbation of the Benjamin Ono equation with periodic boundary conditions on a segment. We consider the case where the perturbation is Hamiltonian and the corresponding Hamiltonian vector field is analytic as a map from the energy space to itself. Let \(\epsilon \) be the size of the perturbation. We prove that for initial data close in energy norm to an N-gap state of the unperturbed equation all the actions of the Benjamin Ono equation remain \({\mathcal {O}}(\epsilon ^{\frac{1}{2(N+1)}})\) close to their initial value for times exponentially long with \(\epsilon ^{-\frac{1}{2(N+1)}}\).