Kepler's problem (around 1706) concerns the motion of a planet around an immovable planet in the presence of the gravitational force. Based on empirical evidence, Kepler stated that the moon moves on an elliptical path around the earth (known as Kepler's first law, and secondly he stated that the position vector of the moving planet sweeps out equal areas in equal time intervals as the planet orbits around the stationary planet (known as Kepler's second law). It was not until Newton's gravitational laws were stated in 1687 (in Principia Mathematica) that Kepler's observations could be verified mathematically.
This lecture is principally motivated by another remarkable discovery that the solutions of Kepler's problem are intimately related to the geometry of spaces of constant curvature. These discoveries go back to V.A. Fock, who in 1935 linked the motion of the hydrogen atom to nonEuclidean Geometry. Then J. Moser, in 1970, showed that Kepler's problem restricted to the manifold of constant negative energy is equivalent to the geodesic flow on the sphere. Finally, Y. Osipov showed in 1977 that Kepler's problem is equivalent to the geodesic flow on the Euclidean space on the energy level zero, and is equivalent to the geodesic flow on the hyperboloid when restricted to the manifold of a constant positive energy.
My lecture will address these "enigmatic" connections between planetary motion and space forms. I will show in this lecture that an ndimensional Kepler's system is equivalent to the geodesic flow on space forms (spaces of constant curvature) precisely under the same conditions as in the paragraph above. I will also show that the famous integrals of motion for the problem of Kepler, the angular momentum and the RungeLenz vector, correspond to a particular moment map associated to the geodesic flow on the appropriate space form.
