Shiqing, Zhang et Qing, Zhou, Symmetric Periodic Noncollision Solutions for N-Body-Type Problems, Acta Mathematica Sinica, New Series Chinese Journal of Mathematics, 11(1), 1995, pp. 37-43
Using the calculus of variations in the large, especially computing the category of the symmetric configuration space of symmetric N-body-type problems, we prove the existence of infinitely many symmetric noncollision periodic solutions about the symmetric and nonau- tonomous N-body-type problems under the assumptions that the symmetric potentials satisfy the strong force condition of Gordon.