Asymptotic symmetries of QED and Weinberg's soft photon theorem

Understand

Various equivalences between so-called soft theorems which constrain scattering amplitudes and Ward identities related to asymptotic symmetries have recently been established in gauge theories and gravity.

• So far these equivalences have been restricted to the case of massless matter fields, the reason being that the asymptotic symmetries are defined at null infinity.
• The restriction is however unnatural from the perspective of soft theorems which are insensitive to the masses of the external particles.
• In this work we remove the aforementioned restriction in the context of scalar QED.