Subleading Soft Theorem for arbitrary number of external soft photons and gravitons

TL;DR

This paper derives a comprehensive subleading soft theorem for multiple soft photons and gravitons in quantum gravity, valid across various spacetime dimensions and loop orders, with implications for classical radiation decoupling.

Contribution

It provides the first unified subleading soft theorem for multiple soft photons and gravitons applicable in multiple spacetime dimensions and loop levels.

Findings

The theorem is valid at tree level in 4D and 5D, and at all loops in higher dimensions.

Low energy photon and graviton radiation decouple in the classical limit.

The result generalizes previous soft theorems to multiple soft particles with arbitrary mass and spin.

Abstract

We obtain the subleading soft theorem for a generic theory of quantum gravity, for arbitrary number of soft photons and gravitons and for arbitrary number of finite energy particles with arbitrary mass and spin when all the soft particles are soft in the same rate. This result is valid at tree level for spacetime dimensions equal to four and five and to all loops in spacetime dimensions greater than five. We verify that in classical limit low energy photon and graviton radiation decouple from each other.