Neumann-type boundary value problem associated with Hamiltonian systems

The aim of this paper is to investigate some multiplicity results for a Hamiltonian system with Neumann-type boundary conditions. A critical point theory is applied in order to show that the the problem has multiple solutions. The crucial part of this paper is that, in contrast to periodic problems where the Poincaré-Birkhoff Theorem has a significant role, no twist condition is required.