IMPULSIVE GRAVITATIONAL-WAVES GENERATED BY NULL PARTICLES IN DESITTERAND ANTI-DE-SITTER BACKGROUNDS

By boosting the metric of the Schwarzschild-de Sitter and Schwarzschil d-anti-de Sitter space-times in the ultrarelativistic limit as the mas s parameter vanishes, impulsive gravitational waves are obtained in ba ckgrounds with a nonzero cosmological constant. We determine the geome try of these impulsive wave surfaces using various coordinate charts. In the de Sitter background they are spheres containing two null parti cles located at the poles. In the anti-de Sitter background they are h yperboloidal surfaces of constant negative curvature containing a sing le null particle on the axis of symmetry. The global structure and con formal diagrams for the complete manifolds are also determined. [S0556 -2821 (97)04620-1]. PACS number(s): 04.20.Jb, 04.30.Nk.