Extended Massive Ambitwistor String

TL;DR

This work extends the massive ambitwistor string to a unified, anomaly-free framework that captures both $N=8$ supergravity and Coulomb-branch SYM within a single BRST-quantized Lagrangian. It demonstrates that all-multiplicity tree and one-loop amplitudes exhibit proper unitary factorization and that the massless limit yields Einstein-Yang-Mills amplitudes, with Compton scattering tests aligning with established results. The cosmological constant is argued to vanish to all orders in perturbation theory, and the one-loop construction is shown to factorize under both non-separating and separating degenerations in a modular-invariant setting. The paper also explores Compton scattering as a consistency check and outlines future work on higher-loop factorization, IR renormalization, and the interpretation of auxiliary spinors and extra bosonic degrees of freedom.

Abstract

This work considers a variation of the massive ambitwistor string model presented in arXiv:2301.11227 that describes supergravity and super-Yang-Mills on the Coulomb branch simultaneously with a single Lagrangian. All-multiplicity tree and one-loop amplitudes are evaluated and shown to have proper unitary factorization. The massless limit provides Einstein Yang-Mills Amplitudes including multiple gluon traces. It is argued that the cosmological constant vanishes at all orders of perturbation theory. As application, results for Compton scattering are obtained and compared with ones in the literature.