The Cosmological Memory Effect

Understand

The "memory effect" is the permanent change in the relative separation of test particles resulting from the passage of gravitational radiation.

• We investigate the memory effect for a general, spatially flat FLRW cosmology by considering the radiation associated with emission events involving particle-like sources.
• We find that if the resulting perturbation is decomposed into scalar, vector, and tensor parts, only the tensor part contributes to memory.
• Furthermore, the tensor contribution to memory depends only on the cosmological scale factor at the source and observation events, not on the detailed expansion history of the universe.