Gravitational memory in the bulk

Understand

A method for detecting gravitational memory is proposed.

• It makes use of ingoing null geodesics instead of timelike geodesics in the original formulation by Christodoulou.
• It is argued that the method is applicable in the bulk of a spacetime.
• In addition, it is shown that BMS symmetry generators in Newman-Unti gauge have an interpretation in terms of the memory effect.