Infrared photons and asymptotic symmetries

TL;DR

This paper demonstrates that the universal behavior of infrared photon emissions in scattering processes can be understood as the Ward identity of asymptotic symmetries in gauge theory, linking soft photon emissions to fundamental symmetries.

Contribution

It explicitly shows that the leading soft photon factorization in tree-level amplitudes corresponds to the Ward identity of gauge theory's asymptotic symmetry.

Findings

Soft photon emissions follow universal factorization.

Soft factorization relates to asymptotic gauge symmetries.

Tree-level amplitudes exhibit this symmetry correspondence.

Abstract

S-matrix elements exhibit universal factorization when multiple infrared photons are emitted in scattering processes. We explicitly show that the leading soft factorization of tree-level amplitudes with the emission of any number of soft photons can be interpreted as the Ward identity of the asymptotic symmetry of gauge theory.