Geodesic congruences, impulsive gravitational waves, and gravitational memory

摘要

In this paper we introduce a new approach to the study of the effects that an impulsive wave, containing a mixture of material sources and gravitational waves, has on a geodesic congruence that traverses it.We find that the effect of the wave on the congruence is a discontinuity in the B-tensor of the congruence. Our results thus provide a detector-independent and covariant characterization of gravitational memory.We note some similarities between our results and the study of soft gravitons and gravitational memory on I.