Two theorems about the existence of periodic solutions with prescribed energy for second order Hamiltonian systems are obtained. One gives existence for almost all energies under very natural conditions. The other yields existence for all energies under a further condition.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-ap105-1-1, author = {Chengfu Che and Xiaoping Xue}, title = {Periodic solutions for second order Hamiltonian systems on an arbitrary energy surface}, journal = {Annales Polonici Mathematici}, volume = {105}, year = {2012}, pages = {1-12}, zbl = {1264.34077}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-ap105-1-1} }
Chengfu Che; Xiaoping Xue. Periodic solutions for second order Hamiltonian systems on an arbitrary energy surface. Annales Polonici Mathematici, Tome 105 (2012) pp. 1-12. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-ap105-1-1/