Gravitational Memory in Numerical Relativity: Computing Memory Effects and Correcting Existing Waveforms

Gravitational memory is a phenomenon induced by the passage of gravitational waves that corresponds to persistent, physical changes to spacetime. We present advances in resolving the two primary gravitational memory effects---displacement and spin memory---in numerical simulations of binary black hole mergers produced by SXS's Spectral Einstein Code. We show that the waveforms extracted using Cauchy-characteristic extraction (CCE) obey the Bondi-Metzner-Sachs (BMS) balance laws to a high degree of accuracy, unlike previous waveforms produced by numerical relativity simulations. We also show that the waveforms in all publicly available waveform catalogs, which do not exhibit memory effects, can be corrected to include such features.