Soft Photon and Graviton Theorems in Effective Field Theory

Understand

Extensions of the photon and graviton soft theorems are derived in 4d local effective field theories with massless particles of arbitrary spin.

• We prove that effective operators can result in new terms in the soft theorems at subleading order for photons and subsubleading order for gravitons.
• The new soft terms are unique and we provide a complete classification of all local operators responsible for such modifications.
• We show that no local operators can modify the subleading soft graviton theorem.