Extended Massive Ambitwistor String II

Abstract

This article continues previous work done in arXiv:2406.01907. It is shown in more detail how vacuum partition functions and the cosmological constant vanish at all orders of perturbation theory. Further, all-multiplicity higher-loop amplitudes are given and shown to be modular invariant, to have proper factorization, and to be UV-finite at least up to one-loop level, formally even to all levels. Therefore, the model provides a modular invariant and unitary N=8 supergravity theory in twistor space with embedded Super-Yang-Mills and promising UV-finiteness behavior.