Vlasenko–Zwegers conjectural identities for the rank two Example 10 Nahm sums

Let qq be a formal variable, and let Ja,bJ_{a,b} and JaJ_a denote the Jacobi-product notation used in the source. Vlasenko–Zwegers' conjecture. The following identities are conjectured:

i,j0q2i2+2ij+2j22ij(q3;q3)i(q3;q3)j=1J3(2J18,45+qJ12,45+q4J3,45),\sum_{i,j\geq 0} \frac{q^{2i^2+2ij+2j^2-2i-j}}{(q^3;q^3)_i(q^3;q^3)_j}=\frac{1}{J_3}\left(2J_{18,45}+qJ_{12,45}+q^4J_{3,45}\right), i,j0q2i2+2ij+2j2(q3;q3)i(q3;q3)j=1J3(J21,45q3J6,45+2q2J9,45).\sum_{i,j\geq 0} \frac{q^{2i^2+2ij+2j^2}}{(q^3;q^3)_i(q^3;q^3)_j}=\frac{1}{J_3}\left(J_{21,45}-q^3J_{6,45}+2q^2J_{9,45}\right).

Equivalently, the source also gives the corresponding bilateral theta-series expressions preceding these product forms. The identities concern modular rank-two Nahm sums; the supplied context says their modularity was confirmed, but describes the identities themselves as conjectural and does not provide a complete proof.

Sources & referencesView supporting material

Primary source

Liuquan Wang, “Identities on Zagier's rank two examples for Nahm's problem”, arXiv:2210.10748 (2024).

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