Constructing Gravity Amplitudes from Real Soft and Collinear Factorisation

TL;DR

This paper develops a method to construct gravity amplitudes using soft and collinear factorisation, introducing 'soft-lifting' functions to generate tree and one-loop amplitudes in N=4 supergravity, with a novel diagrammatic interpretation.

Contribution

It generalizes 'half-soft' functions to 'soft-lifting' functions and applies them to derive gravity amplitudes, including rational terms, with a new diagrammatic perspective.

Findings

Constructed tree-level MHV amplitudes in N=4 supergravity.

Derived rational terms in one-loop amplitudes.

Provided a diagrammatic interpretation of rational terms.

Abstract

Soft and collinear factorisations can be used to construct expressions for amplitudes in theories of gravity. We generalise the "half-soft" functions used previously to "soft-lifting" functions and use these to generate tree and one-loop amplitudes. In particular we construct expressions for MHV tree amplitudes and the rational terms in one-loop amplitudes in the specific context of N=4 supergravity. To completely determine the rational terms collinear factorisation must also be used. The rational terms for N=4 have a remarkable diagrammatic interpretation as arising from algebraic link diagrams.