Integral cohomology and non-isomorphism conjecture for generalized roofs

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For n=2k+1n=2k+1, let Y1Y_1 and Y2Y_2 be the two smooth Calabi–Yau varieties arising as the zero loci in the generalized roof construction, each of dimension k2−1k^2-1.

Integral cohomology and non-isomorphism conjecture. One has an isomorphism of integral cohomology groups

Hk2−1(Y1,Z)≅Hk2−1(Y2,Z),H^{k^2-1}(Y_1,\mathbb{Z})\cong H^{k^2-1}(Y_2,\mathbb{Z}),

but, generically, the varieties are not isomorphic:

Y1≇Y2.Y_1\not\cong Y_2.

The preceding theorem gives the corresponding rational cohomology isomorphism, while the integral statement and generic non-isomorphism are posed as a conjecture. The k=2k=2 case is known to provide a derived-equivalent, non-birational example, whereas the general case remains unresolved in the supplied text.

References

Primary source

Enrico Fatighenti, Michał Kapustka, Giovanni Mongardi and Marco Rampazzo, “The generalized roof F(1,2,n): Hodge structures and derived categories”, arXiv:2110.10475 (2022).

Additional references

4 papers in this index state this conjecture (1998–2021). The statement above is taken from the most recent of them; the others are arXiv:2105.04214, arXiv:1005.2778, arXiv:math/9806143.

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