Asymptotic Symmetries and Electromagnetic Memory
Sabrina Pasterski
TL;DR
The paper completes the triad linking asymptotic U(1) gauge symmetries, leading soft factors, and memory effects for electromagnetism at null infinity. It derives the radiation-zone structure of Maxwell theory, establishes the memory as a time-integrated radiated field, and shows its precise relation to Weinberg's leading soft factor. It then situates memory within the asymptotic large U(1) symmetry framework, detailing boundary conditions and Ward identities, and discusses massive vs massless contributions and potential experimental manifestations. Overall, the work clarifies how zero-mode (memory) observables encode the soft and symmetry data, providing a coherent classical-quantum bridge and suggesting measurable signatures such as velocity kicks or dissipative displacements in viscous media.
Abstract
Recent investigations into asymptotic symmetries of gauge theory and gravity have illuminated connections between gauge field zero-mode sectors, the corresponding soft factors, and their classically observable counterparts -- so called "memories." Here we complete this triad for the case of large U(1) gauge symmetries at null infinity.