English

On exotic modular tensor categories

Geometric Topology 2008-06-10 v3 Category Theory Quantum Algebra

Abstract

It has been conjectured that every (2+1)(2+1)-TQFT is a Chern-Simons-Witten (CSW) theory labelled by a pair (G,λ)(G,\lambda), where GG is a compact Lie group, and λH4(BG;Z)\lambda \in H^4(BG;Z) a cohomology class. We study two TQFTs constructed from Jones' subfactor theory which are believed to be counterexamples to this conjecture: one is the quantum double of the even sectors of the E6E_6 subfactor, and the other is the quantum double of the even sectors of the Haagerup subfactor. We cannot prove mathematically that the two TQFTs are indeed counterexamples because CSW TQFTs, while physically defined, are not yet mathematically constructed for every pair (G,λ)(G,\lambda). The cases that are constructed mathematically include: 1. GG is a finite group--the Dijkgraaf-Witten TQFTs; 2. GG is torus TnT^n; 3. GG is a connected semi-simple Lie group--the Reshetikhin-Turaev TQFTs. We prove that the two TQFTs are not among those mathematically constructed TQFTs or their direct products. Both TQFTs are of the Turaev-Viro type: quantum doubles of spherical tensor categories. We further prove that neither TQFT is a quantum double of a braided fusion category, and give evidence that neither is an orbifold or coset of TQFTs above. Moreover, representation of the braid groups from the half E6E_6 TQFT can be used to build universal topological quantum computers, and the same is expected for the Haagerup case.

Keywords

Cite

@article{arxiv.0710.5761,
  title  = {On exotic modular tensor categories},
  author = {Seung-moon Hong and Eric Rowell and Zhenghan Wang},
  journal= {arXiv preprint arXiv:0710.5761},
  year   = {2008}
}

Comments

Minor changes and addition of a few references. To appear in the special volume of CCM dedicated to Xiao-Song Lin

R2 v1 2026-06-21T09:38:10.056Z