Non-planar minimizers and rotational symmetry in the N-body problem

The Newtonian N-body problem admits uniformly rotating relative equilibrium solutions in the plane, but not in R-3. When the bodies are allowed to interact in R3, is it preferable, in terms of action, to leave the plane and follow a non-planar trajectory? We use the variational techniques of Chenciner and Venturelli (Celestial Mech. Dyn. Astro. 77 (2000) 139) to show that for an open set of masses, there is a class of collision-free, action-minimizing orbits of certain rotational symmetry in the four-body problem which are non-coplanar, i.e. the planar relative equilibrium is not the least-action solution among orbits in R3. Both periodic and quasi-periodic solutions are constructed in this way. We also discuss constructing collision-free action-minimizing solutions possessing d-rotational symmetry along with various other symmetry constraints. (c) 2004 Elsevier Inc. All rights reserved.