Abstract. The first order Hamiltonian system is considered with T-periodic Hamiltonian that is sub-quadratic at infinity. Two kinds of sub-quadraticity are considered. The existence of T-periodic solution is proved using variational methods.
2000 Mathematics Subject Classification. 34C25, 47H15, 58E05, 58F05, 70H30.
Key words and phrases. Critical point, Palais-Smale-Cerami condition, Hamiltonian system, periodic solution.