Integrable Deformations from Twistor Space

TL;DR

This paper unifies different approaches to integrable 2D field theories via 6D holomorphic Chern-Simons on twistor space, introducing a family of deformed sigma models including the lambda-deformation.

Contribution

It provides the first complete description of a family of integrable theories from 6D twistor space, extending beyond previous boundary condition limitations.

Findings

Constructed a novel 4D integrable field theory from 6D holomorphic Chern-Simons.

Derived a multi-parameter 2D integrable model including the lambda-deformation.

Unified different reduction approaches to recover the same integrable models.

Abstract

Integrable field theories in two dimensions are known to originate as defect theories of 4d Chern-Simons and as symmetry reductions of the 4d anti-self-dual Yang-Mills equations. Based on ideas of Costello, it has been proposed in work of Bittleston and Skinner that these two approaches can be unified starting from holomorphic Chern-Simons in 6 dimensions. We provide the first complete description of this diamond of integrable theories for a family of deformed sigma models, going beyond the Dirichlet boundary conditions that have been considered thus far. Starting from 6d holomorphic Chern-Simons theory on twistor space with a particular meromorphic 3-form $\Omega$, we construct the defect theory to find a novel 4d integrable field theory, whose equations of motion can be recast as the 4d anti-self-dual Yang-Mills equations. Symmetry reducing, we find a multi-parameter 2d integrable model, which specialises to the $\lambda$-deformation at a certain point in parameter space. The same model is recovered by first symmetry reducing, to give 4d Chern-Simons with generalised boundary conditions, and then constructing the defect theory.