Ambitwistor strings in six and five dimensions

A bstract Ambitwistor strings are chiral (holomorphic) whose target is the space of complex null geodesics, ambitwistor space. We introduce twistor representations in 6 and 5 dimensions. In 6d representation naturally conformally invariant. Anomaly cancellation leads to models that describe biadjoint scalar amplitudes certain invariant gauge gravity theories, respectively 4 th order. There three such models, reflecting triality for conformal group SO(8) associated these models. On reduction five dimensions, anomaly requires supersymmetry resulting maximally supersymmetric Yang-Mills gravity. The lead formulæ based on polarized scattering equations 5d, found earlier by first two authors.