Four Dimensional Anomaly-Free Twistor String
arXiv:2004.04842
Abstract
This paper presents a covariant twistor string model in four dimensions coupled to two-dimensional worldsheet gravity with an anomaly-free BRST charge. The model contains two twistors and two fermionic bi-spinors with incidence related gauge symmetries and an SU(2) gauge symmetry between the twistors. It is shown that the model leads to familiar gravitational NMHV amplitudes and has modular-invariant one-loop amplitudes.
18 pages