Asymptotic motions converging to arbitrary dynamics for time-dependent Hamiltonians

Abstract

In a previous work [Asymptotically quasiperiodic solutions for time-dependent Hamiltonians, arXiv preprint arXiv:2211.06623 (2022)], we consider time-dependent perturbations of a Hamiltonian having an invariant torus supporting quasiperiodic solutions. Assuming the perturbation decays polynomially fast as time tends to infinity, we prove the existence of an asymptotic KAM torus. That is a time-dependent family of embedded tori converging as time tends to infinity to the quasiperiodic invariant torus of the unperturbed system. In this paper, the dynamic on the invariant torus associated with the unperturbed Hamiltonian is arbitrary. Therefore, we need to assume exponential decay in time in order to prove the existence of a time-dependent family of embedded tori converging in time to the invariant torus associated with the unperturbed system. The proof relies on the implicit function theorem, and the most complicated and original part rests on the solution of the associated linearized problem.