Asymptotic Symmetries and Subleading Soft Photon Theorem in Effective Field Theories

TL;DR

This paper extends the connection between asymptotic symmetries and the subleading soft photon theorem from massless QED to general effective field theories with photons and massless particles, revealing new symmetry charges influenced by three-point functions and irrelevant operators.

Contribution

It demonstrates that the subleading soft photon theorem in any effective field theory is linked to asymptotic symmetries, generalizing previous results beyond massless QED.

Findings

Charges depend on three-point functions.

Irrelevant operators modify symmetry charges.

Soft photon theorem relates to asymptotic symmetries.

Abstract

In [1,2] it was shown that the subleading soft photon theorem in tree level amplitudes in massless QED is equivalent to a new class of symmetries of the theory parameterized by a vector field on the celestial sphere. In this paper, we extend these results to the subleading soft photon theorem in any Effective Field Theory containing photons and an arbitrary spectrum of massless particles. We show that the charges associated to the above class of symmetries are sensitive to certain three point functions of the theory and are corrected by irrelevant operators of specific dimensions. Our analysis shows that the subleading soft photon theorem in any tree level scattering amplitude is a statement about asymptotic symmetries of the ${\cal S}$-matrix.