Wang's maximal-Betti-number conjecture for smooth Calabi-Yau varieties

Let W(n)W^{(n)} be the smooth, projective Calabi-Yau nn-fold constructed in the paper, and write bi(W(n))b_i(W^{(n)}) for its Betti numbers and χ(W(n))\chi(W^{(n)}) for its Euler characteristic.

Wang's maximal-Betti-number conjecture. The variety W(n)W^{(n)} has the largest sum of Betti numbers among smooth, projective Calabi-Yau nn-folds. When nn is odd, it also has the smallest negative Euler characteristic among such varieties.

The conjecture is motivated by the analogous orbifold Betti-number calculation of Esser, Totaro, and Wang and by Yasuda's result relating orbifold cohomology to the cohomology of a crepant resolution. Its general validity remains open.

Sources & referencesView supporting material

Primary source

Jas Singh, “Smooth Calabi-Yau varieties with large index and Betti numbers”, arXiv:2502.07031 (2026).

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