New Double Soft Emission Theorems

TL;DR

This paper investigates double soft emission theorems at tree level across various theories, revealing subleading behaviors controlled by angular momentum and providing compact formulas for leading terms, supported by CHY representation methods.

Contribution

It introduces new double soft emission theorems, including subleading terms, for multiple theories using CHY representations, expanding understanding of soft limits in quantum field theory.

Findings

Subleading double soft scalar emission terms involve angular momentum operators.

A compact formula for leading double soft photon emission is derived.

Theorems are validated across theories like Galileon, DBI, and Yang-Mills-Scalar.

Abstract

We study the behavior of the tree-level S-matrix of a variety of theories as two particles become soft. By analogy with the recently found subleading soft theorems for gravitons and gluons, we explore subleading terms in double soft emissions. We first consider double soft scalar emissions and find subleading terms that are controlled by the angular momentum operator acting on hard particles. The order of the subleading theorems depends on the presence or not of color structures. Next we obtain a compact formula for the leading term in a double soft photon emission. The theories studied are a special Galileon, DBI, Einstein-Maxwell-Scalar, NLSM and Yang-Mills-Scalar. We use the recently found CHY representation of these theories in order to give a simple proof of the leading order part of all these theorems