The Stability of Subharmonic Solutions for Hamiltonian Systems

In this paper, by using the dual Morse index theory, we study the stability of subharmonic solutions of the non-autonomous Hamiltonian systems. We obtain a (infinite) sequence of geometrically distinct periodic solutions such that every element has at most one direction of instability (i.e., it has at least 2n − 2 Floquet multipliers lying on the unit circle in the complex plane if the periodic solution is non-degenerate) or it is elliptic (all its 2n Floquet multipliers are lying on the unit circle) if the periodic solution is degenerate.