# Large gauge transformation and little group for soft photons

## TL;DR

This paper reveals that large gauge transformations in quantum electrodynamics are equivalent to the gauged little group for soft photons, linking residual gauge symmetries to the Euclidean group and providing new insights into soft theorems.

## Contribution

It demonstrates that large gauge transformation charges correspond to non-compact generators of the Euclidean group, connecting residual gauge symmetries with the little group for massless particles.

## Key findings

- LGT charges form part of the Euclidean group generators.
- LGT provides an alternative description of the gauged little group.
- The work clarifies the symmetry structure underlying soft photon theorems.

## Abstract

Recently, large gauge transformation (LGT), the residual gauge symmetry after gauge fixing that survives at null infinity, has drawn much attention concerning soft theorems and the memory effect. We point out that LGT charges in quantum electrodynamics are in fact one of non-compact generators of the two dimensional Euclidean group. Moreover, by comparing two equivalent descriptions of gauge transformation, we suggest that LGT is simply another way of describing the gauged little group for massless soft photons.