Rotating, stationary, axially symmetric spacetimes with collisionless   matter
  The existence of stationary solutions to the Einstein-Vlasov system which are axially symmetric and have non-zero total angular momentum is shown. This provides mathematical models for rotating, general relativistic and asymptotically flat non-vacuum spacetimes. If angular momentum is allowed to be non-zero, the system of equations to solve contains one semilinear elliptic equation which is singular on the axis of rotation. This can be handled very efficiently by recasting the equation as one for an axisymmetric unknown on $\R^5$. 
H{\aa}kan Andr\'easson, Markus Kunze and Gerhard Rein
gr-qc math-ph math.MP