MULTIPLICITY RESULTS FOR THE PERIODIC SOLUTIONS OF THE NONLINEAR HAMILTONIAN SYSTEMS

We investigate the multiplicity of $2{\pi}$-periodic solutions of the nonlinear Hamiltonian system with almost polynomial and exponential potentials, $\dot{z}=J(G^{\prime}(z)+h(t))$, where $z:R{\rightarrow}R^{2n}$, $\dot{z}=\frac{dz}{dt}$, $J=\(\array{0&-I\\I&o}\)$, I is the identity matrix on $R^n$, $H:R^{2n}{\rightarrow}R$, and $H_z$ is the gradient of H. We look for the weak solutions $z=(p,q){\in}E$ of the nonlinear Hamiltonian system.