Mizuno's duality conjecture for modular Nahm quadruples

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Let D=diag⁡(d1,…,dr)D=\operatorname{diag}(d_1,\dots,d_r) with d1,…,dr∈Z>0d_1,\dots,d_r\in\mathbb{Z}_{>0}, let A∈Qr×rA\in\mathbb{Q}^{r\times r} be symmetrizable with symmetrizer DD, meaning that ADAD is symmetric positive definite, let B∈QrB\in\mathbb{Q}^r, and let C∈QC\in\mathbb{Q}. If the generalized Nahm sum associated with (A,B,C,D)(A,B,C,D) is modular, call (A,B,C,D)(A,B,C,D) a modular quadruple. Define

A⋆=A−1,B⋆=A−1B,C⋆=12BT(AD)−1B−tr⁡D24−c,D⋆=D.A^\star=A^{-1},\qquad B^\star=A^{-1}B,\qquad C^\star=\frac{1}{2}B^\mathrm{T}(AD)^{-1}B-\frac{\operatorname{tr}D}{24}-c,\qquad D^\star=D.

Mizuno's duality conjecture. If (A,B,C,D)(A,B,C,D) is a modular quadruple, then (A⋆,B⋆,C⋆,D⋆)(A^\star,B^\star,C^\star,D^\star) is also a modular quadruple.

This generalizes Zagier's proposed duality from Nahm triples to symmetrizable matrices and generalized Nahm sums. The source attributes the conjecture to Mizuno; the supplied material gives no resolution, so its status is recorded as open.

References

Primary source

Liuquan Wang, “Counterexamples to Zagier's Duality Conjecture on Nahm Sums”, arXiv:2411.09701 (2025).

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