Electromagnetic Fields in Kerr-Shild Space-Times
  Making use of twistor structures and the Kerr theorem for shear-free null geodesic congruences, an infinite family of electromagnetic fields satisfying the homogeneous Maxwell equations in flat Minkowski and the associated curved Kerr-Schild backgrounds is obtained for any such congruence in a purely algebraic way. Simple examples of invariant axisymmetric Maxwell fields are presented. 
Vladimir V. Kassandrov
gr-qc hep-th math-ph math.MP