Soft collinear effective theory for gravity

TL;DR

This paper develops a Soft Collinear Effective Theory (SCET) framework for gravity, revealing simplified structures in gravitational amplitudes and manifest symmetries, which could advance understanding of gravitational scattering at various limits.

Contribution

It constructs a gravity SCET at leading and next-to-leading powers, highlighting manifest symmetries and simplifying amplitude calculations compared to full theory.

Findings

Manifest soft graviton theorem and decoupling at leading power

Simplified amplitude structures at next-to-leading power

Constraints from multiple diffeomorphism invariances

Abstract

We present how to construct a Soft Collinear Effective Theory (SCET) for gravity at the leading and next-to-leading powers from the ground up. The soft graviton theorem and decoupling of collinear gravitons at the leading power are manifest from the outset in the effective symmetries of the theory. At the next-to-leading power, certain simple structures of amplitudes, which are completely obscure in Feynman diagrams of the full theory, are also revealed, which greatly simplifies calculations. The effective lagrangian is highly constrained by effectively multiple copies of diffeomorphism invariance that are inevitably present in gravity SCET due to mode separation, an essential ingredient of any SCET. Further explorations of effective theories of gravity with mode separation may shed light on lagrangian-level understandings of some of the surprising properties of gravitational scattering amplitudes. A gravity SCET with an appropriate inclusion of Glauber modes may serve as a powerful tool for studying gravitational scattering in the Regge limit.