ℓ-independent Lefschetz standard conjecture in degree i

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Let XX be a smooth projective variety of dimension nn over an algebraically closed field kk, let h∈CH⁡1(X)h\in \operatorname{CH}^1(X) be the first Chern class of an ample line bundle, let 0≤i≤n0\leq i\leq n, and for every prime ℓ≠char⁡(k)\ell\neq\operatorname{char}(k) define

Lℓn−i=(−)∪hn−i:Heˊti(X,Qℓ)→Heˊt2n−i(X,Qℓ).L_{\ell}^{n-i}=(-)\cup h^{n-i}:\mathrm{H}^i_{\mathrm{\acute{e}t}}(X,\mathbf{Q}_{\ell})\to\mathrm{H}^{2n-i}_{\mathrm{\acute{e}t}}(X,\mathbf{Q}_{\ell}).

ℓ-independent Lefschetz standard conjecture in degree ii. For XX, hh, and ii as above, there exists a codimension ii cycle λ∈CH⁡i(X×X)Q\lambda\in \operatorname{CH}^i(X\times X)_{\mathbf{Q}} such that for every prime ℓ≠char⁡(k)\ell\neq\operatorname{char}(k) the induced map

λ∗:Heˊt2n−i(X,Qℓ)→Heˊti(X,Qℓ)\lambda^*:\mathrm{H}_{\mathrm{\acute{e}t}}^{2n-i}(X,\mathbf{Q}_{\ell})\to\mathrm{H}_{\mathrm{\acute{e}t}}^{i}(X,\mathbf{Q}_{\ell})

is the inverse of Lℓn−iL_{\ell}^{n-i}.

This is the étale-cohomological analogue of the Lefschetz standard conjecture and supplies the motivic input for the paper's results over arbitrary algebraically closed fields. Its general status is open.

References

Primary source

Aise Johan de Jong and Alexander Perry, “The period-index problem and Hodge theory”, arXiv:2212.12971 (2022).

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