Factorized soft graviton theorems at loop level

Understand

We analyze the low-energy behavior of scattering amplitudes involving gravitons at loop level in four dimensions.

• The single-graviton soft limit is controlled by soft operators which have been argued to separate into a factorized piece and a non-factorizing infrared divergent contribution.
• In this note we show that the soft operators responsible for the factorized contributions are strongly constrained by gauge and Poincare invariance under the assumption of a local structure.
• We show that the leading and subleading orders in the soft-momentum expansion can not receive radiative corrections.