Aug 6, 2024

- The lecture discusses scattering events and memory effects in the context of gravitational waves.
- Focus on the relationship between incoming and outgoing measurements and the physical implications.

- The memory effect is defined as the difference between measurements at different times (e.g., at time u=0 and u=10).
- Measurements are taken at future null infinity (scry+) to analyze the effect of incoming data.
- Important to consider assumptions about initial data from scry-.

- Observations made by far away observers in a static frame where galaxies have relatively slow motion.
- Observers boost to a highly accelerated frame, measure gravitational waves, and return to compare results.
- Defined a suitable coordinate system near scry+ for analysis.

- Introduced affine coordinates along null generators of scry+ and defined further coordinates for the neighborhood.
- The metric in this system resembles familiar forms used in gravitational waves analysis.

- Definition of asymptotic flatness presented, highlighting guiding principles for falloff conditions.
- Conditions necessary for finite charges and the validity of equations of motion at leading order discussed.

- BMS (Bondi-Metzner-Sachs) observers' methodologies to measure gravitational waves and memory effects outlined.
- BMS observers operate under fixed trajectories with respect to the cosmic background.
- Measurements involve distances between mirrors and synchronization of clocks to determine changes induced by gravitational waves.

- The relationship between soft theorems and memory effects is emphasized.
- Clarification that gravitational wave memories are measurable and existentially linked to energy and momentum.
- The impact of gravitational waves on clocks and distances in various observational setups is crucial for understanding the memory effect.

- The discussion concludes with the implications of the findings for current and future gravitational wave observations, including LIGO.
- Recognition of the delicate interplay between classical and quantum mechanical frameworks in understanding gravitational phenomena.

- Further exploration of super translations and their relation to memory effects.
- Investigation into the implications of found results for experimental observables in gravitational wave astronomy.