Electromagnetic Duality and the Electric Memory Effect
Yuta Hamada, Min-Seok Seo, Gary Shiu
TL;DR
The paper analyzes soft photons at null infinity in QED to reveal an $ISO(2)$ algebra formed by the helicity and two non-compact generators, identifying one non-compact generator with the residual large gauge transformation and the other with a dual (magnetic) gauge transformation. It shows that closing the algebra requires a dual generator, yielding a three-generator structure that mirrors the photon’s little group, with the electric (LGT) part acting helicity-universally and the dual (LdGT) part acting helicity-distinguishing. The authors then connect the LGT memory to an observable electric potential difference and propose the electric Aharonov-Bohm effect as a direct probe, outlining a feasible experimental scenario and discussing corrections. They also discuss implications for gravitational memory, suggesting a broader role for dualities in asymptotic symmetries and memory phenomena across gauge theories and gravity.
Abstract
We study large gauge transformations for soft photons in quantum electrodynamics which, together with the helicity operator, form an ISO(2) algebra. We show that the two non-compact generators of the ISO(2) algebra correspond respectively to the residual gauge symmetry and its electromagnetic dual gauge symmetry that emerge at null infinity. The former is helicity universal (electric in nature) while the latter is helicity distinguishing (magnetic in nature). Thus, the conventional large gauge transformation is electric in nature, and is naturally associated with a scalar potential. We suggest that the electric Aharonov-Bohm effect is a direct measure for the electromagnetic memory arising from large gauge transformations.