Periodic solutions to perturbed Kepler problems

As well known (by third Kepler’s law) the Kepler problem has many periodic solutions with minimal period T (for any given T > 0). We will try to understand how many of them survive after a T-periodic external perturbation preserving the Newtonian structure of the equation. In doing this, we will be naturally led to the concept of generalized solution and to the theory of regularization of collisions in Celestial Mechanics. Joint work with Rafael Ortega (Granada) and Lei Zhao (Augsburg).