On the behavior of periodic solutions of planar autonomous Hamiltonian systems with multivalued periodic perturbations

Abstract

Aim of the paper is to provide a method to analyze the behavior of $T$-periodic solutions x_\eps, \eps>0, of a perturbed planar Hamiltonian system near a cycle $x_0$, of smallest period $T$, of the unperturbed system. The perturbation is represented by a $T$-periodic multivalued map which vanishes as \eps\to0. In several problems from nonsmooth mechanical systems this multivalued perturbation comes from the Filippov regularization of a nonlinear discontinuous $T$-periodic term. \noindent Through the paper, assuming the existence of a $T$-periodic solution x_\eps for \eps>0 small, under the condition that $x_0$ is a nondegenerate cycle of the linearized unperturbed Hamiltonian system we provide a formula for the distance between any point $x_0(t)$ and the trajectories x_\eps([0,T]) along a transversal direction to $x_0(t).