Discontinuities and collision of gravitational waves in string theory

Abstract

We examine here discontinuities in the metric, the antisymmetric tensor and the dilaton field which are allowed by conformal invariance. We find that the surfaces of discontinuity must necessarily be null surfaces and shock and impulsive waves are both allowed. We employ our results for the case of colliding plane gravitational waves and we discuss the SL(2,R)XSU(2)/RXR WZW model in the present prespective. In particular, the singularities encountered in this model may be viewed as the result of the mutual focusing of the colliding waves.Comment: 15 pages, Late