Impulsive Signals and Gravitational Memory Effect

This paper is a review of the recently published article by Martin O’Loughlin and Hovhannes Demirchian [1] on covariant description of gravitational memory effect. There, a new approach was introduced to study geodesic congruences and their evolution after traversing impulsive signals, containing a mixture of material sources and gravitational waves. It was shown that the effect of the wave on the congruence is a discontinuity in the $$\mathcal{B}$$ -tensor of the congruence which provides a detector independent and covariant characterization of gravitational memory. It was also shown how different components of the impulsive signal effect the evolution of the congruence in the future.