The Ultrarelativistic Kerr-Geometry and its Energy-Momentum Tensor
  The ultrarelativistic limit of the Schwarzschild and the Kerr-geometry together with their respective energy-momentum tensors is derived. The approach is based on tensor-distributions making use of the underlying Kerr-Schild structure, which remains stable under the ultrarelativistic boost. 
H Balasin and H Nachbagauer