Category of SET orders

TL;DR

This paper introduces the category of SET orders as a comprehensive framework to understand symmetry enriched topological orders, capturing their defects, boundaries, charges, and gauging processes in a unified categorical approach.

Contribution

It defines the category of SET orders for symmetry enriched topological phases, providing a categorical algorithm for gauging and proving its reversibility as Morita-equivalence.

Findings

The category of SET orders encodes all key features of symmetry and topological order interactions.

Gauging in this framework is shown to be reversible via Morita-equivalence.

Explicit data for ungauging processes are provided.

Abstract

We propose the representation principle to study physical systems with a given symmetry. In the context of symmetry enriched topological orders, we give the appropriate representation category, the category of SET orders, which include SPT orders and symmetry breaking orders as special cases. For fusion n-category symmetries, we show that the category of SET orders encodes almost all information about the interplay between symmetry and topological orders, in a natural and canonical way. These information include defects and boundaries of SET orders, symmetry charges, explicit and spontaneous symmetry breaking, stacking of SET orders, gauging of generalized symmetry, as well as quantum currents (SymTFT or symmetry TO). We also provide a detailed categorical algorithm to compute the generalized gauging. In particular, we proved that gauging is always reversible, as a special type of Morita-equivalence. The explicit data for ungauging, the inverse to gauging, is given.