Complex product expansion conjecture for Calabi–Yau threefolds

Let XX be a complex projective Calabi–Yau threefold. For each homology class β\beta and genus g0g\geq 0, let eβ,g(X)e_{\beta,g}(X) be an integer, and define

fg(t)=m0xg,m,0tm.f_g(t)=\sum_{m\geq 0}x_{g,m,0}t^m.

Complex product expansion conjecture. The element (X,t[])Hc0(Zsemi-Fano(Cpx3))[[tH2(X)]](X,t^{[\cdot]})\in H^0_c(\mathcal Z^{\mathrm{semi\textrm{-}Fano}}(\operatorname{Cpx}_3))[[t^{H_2(X)}]] is an infinite product

(X,t[])=βg0fg(tβ)eβ,g(X),(X,t^{[\cdot]})=\prod_\beta\prod_{g\geq 0}f_g(t^\beta)^{e_{\beta,g}(X)},

for unique integer invariants eβ,g(X)Ze_{\beta,g}(X)\in\mathbb Z. This seeks a complex-geometric analogue of the Ionel–Parker product expansion; the existence and uniqueness of these invariants are conjectural in the stated setting.

Sources & referencesView supporting material

Primary source

John Pardon, “Universally counting curves in Calabi–Yau threefolds”, arXiv:2308.02948 (2025).

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