Programme

O.9 -- Oral, VCTP-51

Date: Tuesday, 4 August 2026

Time: 08:50 - 09:10

Gravitational Wave Observables and Soft Factors from Wilson Lines

Karan Fernandes (1), Feng-Li Lin (1) and Chris White (2)

(1) Department of Physics, National Taiwan Normal University, Taiwan (2) School of Physical and Chemical Sciences, Queen Mary University of London, United Kingdom

We derive a Wilson line for gravitationally interacting theories using the Schwinger proper time formalism. A key feature of gravitational Wilson lines is that they can be systematically expanded in terms of multiple soft gravitons, derived from fluctuations about the asymptotic trajectories of the external particles. I will discuss our result for gravitational Wilson lines up to double soft graviton order. This will be shown to recover the known double soft graviton factor for scattering amplitudes, and a new universal double soft graviton factor at subleading order in the momentum expansion. The Wilson lines can also be expressed in terms of radiative graviton modes to provide a dressing operator. I will discuss how this operator can be used to derive non-linear radiative observables from binary black hole interactions. In particular, I will discuss our result for the gravitational waveform and show that it recovers the non-linear memory effect sourced by low frequency emissions.

Presenter: Fernandes Karan