Stable dynamics in forced systems with sufficiently high/low forcing frequency

TL;DR

This paper investigates the stability of parametrically forced Hamiltonian systems at high and low forcing frequencies, demonstrating conditions under which the dynamics remain stable even with large forcing amplitudes.

Contribution

The study extends the application of KAM theory to high and low frequency forcing regimes with large amplitudes, beyond traditional perturbation limits.

Findings

KAM theorem applies at high forcing frequencies with large amplitudes.

Stable dynamics occur at low frequencies with moderate or large amplitudes.

Numerical simulations confirm stability beyond analytical bounds.

Abstract

We consider a class of parametrically forced Hamiltonian systems with one-and-a-half degrees of freedom and study the stability of the dynamics when the frequency of the forcing is relatively high or low. We show that, provided the frequency of the forcing is sufficiently high, KAM theorem may be applied even when the forcing amplitude is far away from the perturbation regime. A similar result is obtained for sufficiently low frequency forcing, but in that case we need the amplitude of the forcing to be not too large; however we are still able to consider amplitudes of the forcing which are outside of the perturbation regime. Our results are illustrated by means of numerical simulations for the system of a forced cubic oscillator. In addition, we find numerically that the dynamics are stable even when the forcing amplitude is very large (beyond the range of validity of the analytical results), provided the frequency of the forcing is taken correspondingly low.