Appears in collection : Korea-France Joint Workshop on String Theory

I will illustrate the hidden simplicity relating the classical limits of different theories, including $N=8$ supergravity, electrodynamics, and certain scalar theories. Despite this simplicity, extracting observables from the classical limit becomes rapidly computationally expensive at higher orders. This motivates a complementary approach to weak-field gravity, based on the Schwinger–Keldysh path integral, in which the dynamics and waveform are computed for generic relativistic worldlines, bypassing several technical intermediate steps in the computation of gravitational-wave observables.