Tree level amplitudes from soft theorems

TL;DR

This paper shows how tree-level amplitudes and soft factors can be uniquely reconstructed using soft theorems, universality, and the double copy assumption, extending to gravity-related theories.

Contribution

It provides explicit formulas for soft factors and reconstructs various amplitudes, including Yang-Mills, Einstein-Yang-Mills, and gravitational amplitudes, from soft theorems.

Findings

Soft factors for bi-adjoint scalar and gluon are explicitly determined.

Single trace Yang-Mills-scalar and pure Yang-Mills amplitudes are reconstructed.

Extended formulas reproduce soft factors for gravitons in gravitational theories.

Abstract

We demonstrate that the tree level amplitudes and the explicit formulas of soft factors can be uniquely determined by soft theorems and the universality of soft factors. By imposing the soft theorems and the universality, as well as the assumption of double copy, we reconstruct single trace Yang-Millsscalar amplitudes and pure Yang-Mills amplitudes, in the expanded formulas. The explicit formulas of soft factors for the bi-adjoint scalar and gluon are also determined. The expansions of Yang-Mills-scalar and Yang-Mills amplitudes can be extended to Einstein-Yang-Mills and gravitational amplitudes, and we use the expanded single trace Einstein-Yang-Mills amplitudes to reproduce the soft factors for the graviton.