Accurate waveform modelling for LISA requires a rigorous understanding of the asymptotic structure of spacetime. Gravitational wave memory, a persistent, hereditary displacement of observer position, emerges due to gravitational waves emitted during a binary inspiral and merger. Capturing this secular evolution is essential for overall phase accuracy, but it presents a distinct theoretical challenge: waveforms extracted at null infinity are subject to Bondi-Metzner-Sachs (BMS) frame ambiguities. To compare high-accuracy self-force waveforms with other binary modelling techniques, such as numerical relativity and post-Newtonian theory, knowledge of the BMS frame is crucial.
We have developed theoretical frameworks to systematically identify and fix the BMS frame for extreme mass-ratio inspirals, ensuring that our second-order waveforms are physically unambiguous and free from gauge-induced asymptotic artefacts. Using this framework, we have successfully characterised the physical memory for quasi-circular orbits in a Schwarzschild background. Work is now underway to extend these frame-fixing procedures and memory calculations to generic orbits—including high eccentricity and inclination—and to the Kerr background, where the interplay of memory, spin, and resonances demands highly precise asymptotic control.
Current focus:
- Systematic BMS frame-fixing protocols for generic orbits in Schwarzschild and Kerr
- Computation of second-order secular memory effects for astrophysically realistic inspirals
- Aligning self-force asymptotic frames with Numerical Relativity (NR) for high-precision waveform cross-validation
- Assessing the impact of hereditary memory components on LISA parameter estimation