From Torus Bundles to Particle-Hole Equivariantization

TL;DR

This paper explores the construction of (pre)modular tensor categories from 3-manifolds, specifically torus bundles, and shows their realization via particle-hole equivariantization, advancing understanding of topological quantum field theories.

Contribution

It demonstrates that modular data from torus bundles over the circle can be realized through $ ext{Z}_2$-equivariantization of pointed premodular categories, linking topology and category theory.

Findings

Modular data from torus bundles are realized by particle-hole equivariantization.

The construction connects 3-manifold invariants with categorical symmetries.

Provides a class of examples to improve the understanding of modular tensor categories.

Abstract

We continue the program of constructing (pre)modular tensor categories from 3-manifolds first initiated by Cho-Gang-Kim using $M$ theory in physics and then mathematically studied by Cui-Qiu-Wang. An important structure involved is a collection of certain $\text{SL}(2, \mathbb{C})$ characters on a given manifold which serve as the simple object types in the corresponding category. Chern-Simons invariants and adjoint Reidemeister torsions play a key role in the construction, and they are related to topological twists and quantum dimensions, respectively, of simple objects. The modular $S$-matrix is computed from local operators and follows a trial-and-error procedure. It is currently unknown how to produce data beyond the modular $S$- and $T$-matrices. There are also a number of subtleties in the construction which remain to be solved. In this paper, we consider an infinite family of 3-manifolds, that is, torus bundles over the circle. We show that the modular data produced by such manifolds are realized by the $\mathbb{Z}_2$-equivariantization of certain pointed premodular categories. Here the equivariantization is performed for the $\mathbb{Z}_2$-action sending a simple (invertible) object to its inverse, also called the particle-hole symmetry. It is our hope that this extensive class of examples will shed light on how to improve the program to recover the full data of a premodular category.