The representation theory of a conformal net is a unitary modular tensor category. It is captured by the bimodule category of the Jones-Wassermann subfactor. In this paper, we construct multi-interval Jones-Wassermann subfactors for unitary modular tensor categories. We prove that these subfactors are self-dual. It generalizes and categorifies the self-duality of finite abelian groups and we call it modular self-duality. arXiv:1612.08573v3 [math.OA] 8 Jun 2017
ZHENGWEI LIU AND FENG XUThe bimodule category of a subfactor is described by a subfactor planar algebra [Jon98]. The n-box space of the planar algebra of the m-interval Jones-Wassermann subfactor for C is given by the vector space hom C m (1, γ n m ). It turns out to be natural to represent these vectors by a 3D picture. This representation identifies hom C m (1, γ n m ) as a configuration space Conf n,m on a 2D n × m lattice. Therefore the configuration space {Conf n,m } m,n∈N unifies the Jones-Wassermann subfactors for all m ≥ 1. It is a natural candidate for the configuration space of a 2D lattice model that can be used in the reconstruction program.Moreover, we show that planar tangles can act on {Conf n,m } m,n∈N in two different directions independently. In one direction m is fixed. These actions are the usual ones in the planar algebra of the m-interval Jones-Wassermann subfactor. In the other direction n is fixed. These actions relate the Jones-Wassermann subfactor with different intervals which have not been studied before.The bi-directional actions of planar tangles are compatible with the geometric actions on the 2D lattices. We call such family of vector spaces a bi-planar algebra. It is a new subject in subfactor theory and it adds one additional dimension to the theory of planar algebras.This 3D representation also leads to the discovery of a new symmetry between m and n, although the meaning of the actions of planar tangles in the two directions are completely different. It will be interesting to understand these additional symmetries in conformal field theory.When C is the representation category of a finite abelian group G, the configuration space Conf (C ) 2,2 becomes L 2 (G). Moreover, the modular self-duality coincides with the self-duality of G. The proof of the self-duality of G uses the discrete Fourier transform on G. We construct the string Fourier transform (SFT) on the configuration space hom C m (1, γ n m ) to prove the modular self-duality. From this point of view, the modular self-duality and the SFT generalize and categorify the self-duality and the Fourier transform of finite abelian groups.Moreover, the SFT on Conf (C ) 2,2 is the same as the modular S-matrix of C . Therefore we can study the Fourier analysis of the S-matrix on Conf (C ) 2,2 . It fits into the recent progress about the Fourier analysis on subfactors [Liu16, JLW16, LW17, JLW].The modular self-duality has been used in the quon 3D language for quantum information [LWJ], where the vector space hom C 2 (1, γ 2 2 ) is considered as the 1-quon space. A combination ...