Jannsen's generalized Beilinson and semisimplicity conjecture

Let kk be a finite field, let XX be a variety over kk, and let iZi\in\mathbb{Z}. Fix a prime char(k)\ell\neq\operatorname{char}(k), write X\overline{X} for the base change to an algebraic closure, and let Frobq\operatorname{Frob}_q denote geometric Frobenius, where q=kq=\lvert k\rvert. The cycle class map is

CHi(X)QQH2i(X,Q(i))Gk.\operatorname{CH}_i(X)\otimes_{\mathbb{Q}}\mathbb{Q}_{\ell}\to H_{2i}(\overline{X},\mathbb{Q}_{\ell}(i))^{G_k}.

Generalized Beilinson and semisimplicity conjecture. The cycle class map induces an isomorphism, and the eigenvalue 11 of Frobq\operatorname{Frob}_q acting on H2i(X,Q(i))H_{2i}(\overline{X},\mathbb{Q}_{\ell}(i)) is semisimple. In particular,

dimQCHi(X)=ordt=1χ(H2i(X,Q(i)),t).\dim_{\mathbb{Q}}\operatorname{CH}_i(X)=\operatorname*{ord}_{t=1}\chi(H_{2i}(\overline{X},\mathbb{Q}_{\ell}(i)),t).

This is the étale-homological extension of the preceding Tate and Beilinson-type conjectures from smooth varieties to arbitrary varieties over finite fields. The source attributes the formulation to Jannsen; no resolution status is supplied.

Sources & referencesView supporting material

Primary source

Matt Broe, “On the Beilinson-Bloch conjecture over function fields”, arXiv:2505.00696 (2026).

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