Fourier-transformed gauge theory models of three-dimensional topological orders with gapped boundaries

TL;DR

This paper extends Fourier transform techniques to three-dimensional gauge theories, revealing how gapped boundaries are characterized by Frobenius algebras and connecting these models to Walker-Wang models and topological field theories.

Contribution

It introduces a Fourier transform approach for 3D gauge theories, linking them to Walker-Wang models and providing a systematic way to construct gapped boundary theories.

Findings

Gapped boundary conditions characterized by Frobenius algebras in Rep(G)

Fourier transform maps 3D gauge theories to Walker-Wang models

Establishes correspondence between Dijkgraaf-Witten and Crane-Yetter theories

Abstract

In this paper, we apply the method of Fourier transform and basis rewriting developed in arXiv:1910.13441 for the two-dimensional quantum double model of topological orders to the three-dimensional gauge theory model (with a gauge group $G$) of three-dimensional topological orders. We find that the gapped boundary condition of the gauge theory model is characterized by a Frobenius algebra in the representation category $\mathcal Rep(G)$ of $G$, which also describes the charge splitting and condensation on the boundary. We also show that our Fourier transform maps the three-dimensional gauge theory model with input data $G$ to the Walker-Wang model with input data $\mathcal Rep(G)$ on a trivalent lattice with dangling edges, after truncating the Hilbert space by projecting all dangling edges to the trivial representation of $G$. This Fourier transform also provides a systematic construction of the gapped boundary theory of the Walker-Wang model. This establishes a correspondence between two types of topological field theories: the extended Dijkgraaf-Witten and extended Crane-Yetter theories.