The exponent-realization conjecture for modular invariants and NIM-reps

Let C\cal{C} be a modular tensor category of rank kk with modular data SS and TT. A modular invariant is a matrix MM satisfying MS=SMMS=SM, MT=TMMT=TM, MabNM_{ab}\in\mathbb{N} for all simple objects a,ba,b, and M00=1M_{00}=1. Its exponent is the multiset

EM=(\mathds1M00,X1M11,,Xk1Mk1,k1).\mathcal{E}_M=\left(\mathds{1}^{M_{00}},X_1^{M_{11}},\ldots,X_{k-1}^{M_{k-1,k-1}}\right).

A NIM-rep NN associated to C\cal{C} has an exponent E(N)\mathcal{E}(N) obtained from the multiplicities of the eigenvalues Sa,b/S0,bS_{a,b}/S_{0,b} in the matrices NaN_a. Exponent-realization conjecture. For every rational conformal field theory described by a modular tensor category C\cal{C} and every modular invariant MM, there exists a NIM-rep NN such that

E(N)=EM.\mathcal{E}(N)=\mathcal{E}_M.

This proposes that every modular invariant has a NIM-rep realizing the same exponent multiset. The provided text does not state whether the conjecture is known or open.

Sources & referencesView supporting material

Primary source

Samuel Hannah, Ana Ros Camacho and with an appendix with Devi Young, “Reconstructing algebra objects from NIM-reps in pointed, near-group and quantum group-like fusion categories”, arXiv:2312.13796 (2023).

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