Gravitational Waves in String theory in Anti-de Sitter Background
  Inspired by the studies of gravitational waves in anti-de Sitter universe, in general relativity, in this paper we investigate the possibility of similar solutions in IIB string theory on $AdS_3 x S^3 x R^4$. We give a general form for such solutions in this background and present several explicit examples, by directly solving the field equations, as well as the ones obtained by taking a scaling limit on D1-D5 brane systems in a pp-wave background. The form of the metric in our solutions corresponds to a gravitational wave in $AdS_3$. We show the supersymmetric nature of these solutions and discuss the possibility of their generalizations to other anti-de Sitter backgrounds, including the ones in four dimensions. 
Alok Kumar