Abstract

Instead of studying anyon condensation in various concrete models, we take a bootstrap approach by considering an abstract situation, in which an anyon condensation happens in a 2-d topological phase with anyonic excitations given by a modular tensor category C; and the anyons in the condensed phase are given by another modular tensor category D. By a bootstrap analysis, we derive a relation between anyons in D-phase and anyons in C-phase from natural physical requirements. It turns out that the vacuum (or the tensor unit) A in D-phase is necessary to be a connected commutative separable algebra in C, and the category D is equivalent to the category of local A-modules as modular tensor categories. This condensation also produces a gapped domain wall with wall excitations given by the category of A-modules in C. A more general situation is also studied in this paper. We will also show how to determine such algebra A from the initial and final data. Multi-condensations and 1-d condensations will also be briefly discussed. Examples will be given in the toric code model, Kitaev quantum double models, Levin–Wen types of lattice models and some chiral topological phases.

Highlights

  • Instead of studying anyon condensation in concrete models, we take an abstract approach

  • The main goal of this paper is to provide a detailed explanation of how each ingredient of the complete mathematical structures emerge naturally from concrete and natural physical requirements

  • We assume that an anyon condensation happens in a 2d region inside of a 2d phase C as depicted in Fig. 1, and the anyons in the condensed phase form another modular tensor category (MTC) D, which is equipped with a tensor product ⊗D, a tensor unit 1D, an associator αDL,M,N : (L ⊗D M) ⊗D N → − L ⊗D (M ⊗D N), a braiding cDM,N : M ⊗D N → − N ⊗D M and a twist θDM : M → − M for all L, M, N ∈ D

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Summary

Introduction

Anyon condensation is an important subject to study in the field of topological orders. The main goal of this paper is to provide a detailed explanation of how each ingredient of the complete mathematical structures emerge naturally from concrete and natural physical requirements We hope that this analysis can convince physicists that the tensor-categorical language, abstract, is a powerful and necessary language for anyon condensation. The layout of the paper is: in Section 2, we carry out this bootstrap analysis and derive our main results; in Section 3, we discuss how to use physical macroscopic data to determine the condensation; in Section 4, we provide examples; in Section 5, we discuss the Witt equivalence between 2d topological orders; Appendix contains the definitions of all tensor-categorical notions appeared in this work.

Bootstrap analysis
Physical data associated to a condensation
Vacuum in D as an algebra in C
Unit properties
Commutativity
General deconfined particles
The bulk-to-wall map from D-side is given by the central functor
Determining the condensation from physical data
Gapped boundaries
Non-trivial D-phase
Examples
Toric code model
Levin-Wen types of lattice models
Kitaev quantum-double models
Condensations in chiral topological phases
Completely anisotropic 2d phases
Witt equivalence
C AlAo1c and
Modular tensor categories
Algebras in a MTC
Module categories and monoidal centers
Full Text
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