Voisin's integral Hodge/Tate conjecture for one cycles on rationally connected varieties

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Let XX be a smooth projective separably rationally connected variety of dimension dd over an algebraically closed field. The groups

Heˊt⁡2d−2(X,Zl(d−1))H^{2d-2}_{\operatorname{\acute{e}t}}(X, \mathbb{Z}_l(d-1))

and, when XX is defined over the complex numbers,

Hsing⁡2d−2(X,Z)H^{2d-2}_{\operatorname{sing}}(X, \mathbb{Z})

are algebraic. Voisin's integral Hodge/Tate conjecture. Every class in these integral cohomology groups is generated by classes of algebraic cycles. The usual Tate/Hodge conjecture gives algebraicity only for the relevant Galois-invariant or (p,p)(p,p) classes; for separably rationally connected varieties, the corresponding rational cohomology is already algebraic by a decomposition of the diagonal. The integral assertion is known in characteristic zero for threefolds and smooth Fano fourfolds, but remains open in general.

References

Primary source

Zhiyu Tian, “Zero cycles on rationally connected varieties over Laurent fields”, arXiv:2010.04996 (2020).

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