Abstract
Let a, U \in C^2(Ω) where Ω is a bounded set in ℝ^n and let \mathrm{L}\left(x,\xi \right) = \frac{1}{2}a\left(x\right)\left|\xi \right|^{2}−\mathrm{U}\left(x\right),\:\:x \in Ω;\xi \in ℝ^{n}. We suppose that a, U > 0 for x \in Ω and that \lim \limits_{x\rightarrow ∂Ω}\mathrm{U}\left(x\right) = + ∞. Under some smoothness assumptions, we prove that the Lagrangian system associated with the above Lagrangian \mathrm{L} has infinitely many periodic solutions of any period \mathrm{T} .