Nonexpanding impulsive gravitational waves with an arbitrary cosmological constant

Exact solutions for nonexpanding impulsive waves in a background with nonze ro cosmological constant are constructed using a 'cut and paste' method. Th ese solutions are presented using a unified approach which covers the cases of de Sitter, anti-de Sitter and Minkowski backgrounds. The metrics are pr esented in continuous and distributional forms, both of which are conformal to the corresponding metrics for impulsive pp-waves, and for which the lim it as Lambda-->0 can be made explicitly. (C) 1999 Elsevier Science B.V. All rights reserved.