Double Copy of 3D Chern-Simons Theory and 6D Kodaira-Spencer Gravity

TL;DR

This paper constructs a double copy relationship between 3D Chern-Simons theory and 6D Kodaira-Spencer gravity, revealing a topological, gauge-invariant, non-Lagrangian theory that connects lower and higher-dimensional gravity models.

Contribution

It introduces an algebraic double copy framework for 3D Chern-Simons theory leading to a novel topological gravity theory related to 6D Kodaira-Spencer gravity.

Findings

The double copy yields a topological, gauge-invariant theory.

The theory relates 3D Chern-Simons to 6D Kodaira-Spencer gravity.

The non-Lagrangian theory can be made Lagrangian by sacrificing locality.

Abstract

We apply an algebraic double copy construction of gravity from gauge theory to three-dimensional (3D) Chern-Simons theory. The kinematic algebra ${\cal K}$ is the 3D de Rham complex of forms equipped, for a choice of metric, with a graded Lie algebra that is equivalent to the Schouten-Nijenhuis bracket on polyvector fields. The double copied gravity is defined on a subspace of ${\cal K}\otimes \bar{\cal K}$ and yields a topological double field theory for a generalized metric perturbation and two 2-forms. This local and gauge invariant theory is non-Lagrangian but can be rendered Lagrangian by abandoning locality. Upon fixing a gauge this reduces to the double copy of Chern-Simons theory previously proposed by Ben-Shahar and Johansson. Furthermore, using complex coordinates in $\mathbb{C}^3$ this theory is related to six-dimensional (6D) Kodaira-Spencer gravity in that truncating the two 2-forms and one equation yields the Kodaira-Spencer equations on a 3D real slice of $\mathbb{C}^3$. The full 6D Kodaira-Spencer theory can instead be obtained as a consistent truncation of a chiral double copy.