Capturing tail effects in black‑hole dynamics within S‑matrix frameworks

Determine whether long‑range, non‑local‑in‑time tail contributions to gravitational radiation in black‑hole scattering can be captured within S‑matrix‑based approaches, and, if so, develop a consistent method to include these effects.

Background

The S‑matrix is powerful for flat‑space scattering and some gravitational‑wave observables, but certain effects such as tails—arising from long‑distance propagation and backreaction—could lie beyond standard S‑matrix treatments.

The panel flagged uncertainty over the ability of S‑matrix techniques to account for these non‑local‑in‑time contributions, directly impacting predictions for binary dynamics.