A Variational proof of the existence of Von Schubart's orbit

Abstract

Weconsiderthecollinearthree-bodyproblemwithtwoequalmasses for the Newtonian potential $1/r$. We give a rigorous proof of the existence of a symmetric periodic solution with two collisions per period. This solution has been discovered numerically in 1956 by J. von Schubart (see [12]). Our proof is based on the direct method in Calculus of Variations, which consists in the minimization of the action on a well chosen set of periodic loops. The main difficulty is to show that the minimizer has only two collisions per period.