Existence of subharmonic solutions for non-quadratic second-order Hamiltonian systems
Existence of subharmonic solutions for non-quadratic second-order Hamiltonian systems
In this paper, some existence theorems are obtained for subharmonic solutions of second-order Hamiltonian systems with linear part under non-quadratic conditions. The approach is the minimax principle. We consider some new cases and obtain some new existence results. MSC:34C25, 58E50, 70H05.