Connecting the ambitwistor and the sectorized heterotic strings
Thales Azevedo, Renann Lipinski Jusinskas
TL;DR
The paper clarifies the fate of the sectorized heterotic string by introducing a dimensionful length scale $ ext{ extellipsis}$ and formulating two inequivalent sectors (A and B). At finite $ ext{ extellipsis}$, the B model hosts a massive open-string–like multiplet with $M^{2}=4/ ext{ extellipsis}^{2}$, while the A model remains massless; in the $ ext{ extellipsis} o ext{ extellipsis}$ limit, the theory becomes the heterotic ambitwistor string with BRST charge $Q= ext{``} ext{ extellipsis}+rac{1}{4}ar{c}P^{m}P_{m} ext{''}$, recovering Mason–Skinner’s gravity sector and revealing an extra 3-form and related states. The work demonstrates that the ambitwistor string emerges as the tensionless limit of the sectorized model, with a Galilean conformal structure and a nuanced cohomology that includes both massless supergravity and additional massless/massive states, thereby connecting twisted and chiral string theories. It also highlights a potential missing vector degree of freedom relative to Mason–Skinner's spectrum and discusses covariant, light-cone, and DDF-type constructions for the massive sector, laying groundwork for further study of integrated vertices and background couplings in these chiral theories.
Abstract
The sectorized description of the (chiral) heterotic string using pure spinors has been misleadingly viewed as an infinite tension string. One evidence for this fact comes from the tree level 3-point graviton amplitude, which we show to contain the usual Einstein term plus a higher curvature contribution. After reintroducing a dimensionful parameter $\ell$ in the theory, we demonstrate that the heterotic model is in fact two-fold, depending on the choice of the supersymmetric sector, and that the spectrum also contains one massive (open string like) multiplet. By taking the $\ell\to\infty$ limit, we finally show that the ambitwistor string is recovered, reproducing the unexpected heterotic state in Mason and Skinner's RNS description.
