Black-Hole-Wave Duality in String Theory
  Extreme 4-dimensional dilaton black holes embedded into 10-dimensional geometry are shown to be dual to the gravitational waves in string theory. The corresponding gravitational waves are the generalization of pp-fronted waves, called supersymmetric string waves. They are given by Brinkmann metric and the two-form field, without a dilaton. The non-diagonal part of the metric of the dual partner of the wave together with the two-form field correspond to the vector field in 4-dimensional geometry of the charged extreme black holes. 
Eric Bergshoeff, Renata Kallosh and Tomas Ortin