Gravitational Memory, BMS Supertranslations and Soft Theorems

Understand

The transit of a gravitating radiation pulse past arrays of detectors stationed near future null infinity in the vacuum is considered.

• It is shown that the relative positions and clock times of the detectors before and after the radiation transit differ by a BMS supertranslation.
• An explicit expression for the supertranslation in terms of moments of the radiation energy flux is given.
• The relative spatial displacement found for a pair of nearby detectors reproduces the well-known and potentially measurable gravitational memory effect.