Higher-degree denominator conjecture for membrane indices on O(−1)⊕O(3)\mathcal{O}(-1)\oplus\mathcal{O}(3) over P2\mathbb{P}^2

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Let q‾0,q‾1,q‾2\overline{q}_0,\overline{q}_1,\overline{q}_2 be the equivariant variables in the example of the local Calabi–Yau fivefold over P2\mathbb{P}^2, let [H][H] denote the hyperplane class, and let Ωd[H]\Omega_{d[H]} be the corresponding membrane index. For an integer nn, write od⁡(n)\operatorname{od}(n) for its odd part, and let [m]q‾i[m]_{\overline{q}_i} denote the quantum-number notation used for the equivariant variable q‾i\overline{q}_i.

Higher-degree denominator conjecture. For every integer d>1d>1,

(∏i=02∏n=1d−1[2n]q‾i[od⁡(n)]q‾i)⋅Ωd[H]∈Z[e1±1,e2,e3].\left(\prod_{i=0}^2 \prod_{n=1}^{d-1}\frac{[2n]_{\overline{q}_i}}{[\operatorname{od}(n)]_{\overline{q}_i}}\right)\cdot \Omega_{d[H]} \in \mathbb{Z}[e_1^{\pm 1},e_2,e_3].

The claim predicts that, after multiplying by the displayed factors, higher-degree membrane indices have integral coefficients. It is motivated by numerical data and the observation that powers of 22 are the worst denominators in the non-skeletal limit; the source gives no proof or resolution.

References

Primary source

Yannik Schuler, “Gromov-Witten invariants and membrane indices of fivefolds via the topological vertex”, arXiv:2603.24256 (2026).

Additional references

2 papers in this index state this conjecture (2013–2026). The statement above is taken from the most recent of them; the others are arXiv:1310.7904.

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