The n-Body Problem in Spaces of Constant Curvature. Part I: Relative Equilibria

We extend the Newtonian n-body problem of celestial mechanics to spaces of curvature kappa = constant and provide a unified framework for studying the motion. In the 2-dimensional case, we prove the existence of several classes of relative equilibria, including the Lagrangian and Eulerian solutions for any kappa not equal 0 and the hyperbolic rotations for kappa < 0. These results lead to a new way of understanding the geometry of the physical space. In the end we prove Saari's conjecture when the bodies are on a geodesic that rotates elliptically or hyperbolically.