ℓ-independent Lefschetz standard conjecture in degree i

Let XX be a smooth projective variety of dimension nn over an algebraically closed field kk, let hCH1(X)h\in \operatorname{CH}^1(X) be the first Chern class of an ample line bundle, let 0in0\leq i\leq n, and for every prime char(k)\ell\neq\operatorname{char}(k) define

Lni=()hni:Heˊti(X,Q)Heˊt2ni(X,Q).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 λCHi(X×X)Q\lambda\in \operatorname{CH}^i(X\times X)_{\mathbf{Q}} such that for every prime char(k)\ell\neq\operatorname{char}(k) the induced map

λ:Heˊt2ni(X,Q)Heˊti(X,Q)\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 LniL_{\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.

Sources & referencesView supporting material

Primary source

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

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