Notes on the ambitwistor pure spinor string

TL;DR

This paper investigates the ambitwistor pure spinor string, deriving the $b$ ghost, proposing a new BRST charge for heterotic cases, and confirming the cohomology describes heterotic supergravity.

Contribution

It introduces a simplified construction of the $b$ ghost, a new BRST charge proposal for heterotic strings, and verifies the spectrum matches heterotic supergravity.

Findings

Derived the $b$ ghost with properties similar to the pure spinor case

Proposed a new BRST charge for heterotic ambitwistor strings

Confirmed the cohomology describes heterotic supergravity spectrum

Abstract

In this work, some aspects of the ambitwistor pure spinor string are investigated. The $b$ ghost is presented and its main properties are derived in a simple way, very similar to the usual pure spinor $b$ ghost construction. The heterotic case is also addressed with a new proposal for the BRST charge. The BRST cohomology is shown to correctly describe the heterotic supergravity spectrum and a semi-composite $b$ ghost is constructed.