New Periodic Solutions for Second Order Hamiltonian Systems with Local   Lipschitz Potentials
  Firstly,we generalize the classical Palais-Smale-Cerami condition for $C^1$ functional to the local Lipschitz case,then generalize the famous Benci-Rabinowitz's and Rabinowitz's Saddle Point Theorems with classical Cerami-Palais-Smale condition to the local Lipschitz functional, then we apply these Theorems to study the existence of new periodic solutions for second order Hamiltonian systems with local Lipschitz potentials which are weaker than Rabinowitz's original conditions .The key point of our proof is proving Cerami-Palais-Smale condition for local Lipschitz case,which is difficult since no smooth and symmetry for the potential. 
Li Bingyu and Li Fengying and Zhang Shiqing
math.FA