Self-gravitating stationary spherically symmetric systems in   relativistic galactic dynamics
  We study equilibrium states in relativistic galactic dynamics which are described by solutions of the Einstein-Vlasov system for collisionless matter. We recast the equations into a regular three-dimensional system of autonomous first order ordinary differential equations on a bounded state space. Based on a dynamical systems analysis we derive new theorems that guarantee that the steady state solutions have finite radii and masses. 
Mikael Fj\"allborg, J. Mark Heinzle and Claes Uggla