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

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

Heˊt2d2(X,Zl(d1))H^{2d-2}_{\operatorname{\acute{e}t}}(X, \mathbb{Z}_l(d-1))

and, when XX is defined over the complex numbers,

Hsing2d2(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.

Sources & referencesView supporting material

Primary source

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

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