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Tate Conjecture


The Tate conjecture asserts that, for a smooth projective algebraic variety X over a finitely generated field and a prime l distinct from the field characteristic, the classes invariant under the Galois group in its l-adic cohomology are generated by classes of algebraic cycles. In codimension r, it predicts the surjectivity of the cycle-class map after tensoring with Q_l onto the invariant part of H^(2r)(X_(k^_),Q_l(r)).

Over a finite field, the conjecture is related to the order of the pole of the zeta function of X at the point corresponding to codimension r. It is an arithmetic analog of the Hodge conjecture and is known in several important special cases, but remains open in general.

Brantner (2026) proved the integral geometric Tate conjecture for ordinary Calabi-Yau varieties of dimension three over finite fields. Here ordinary means that its Hodge and Newton polygons agree. The result also holds for 1-ordinary threefolds with H^1(X,O_X)=H^2(X,O_X)=0. Here "integral" means using the l-adic integers Z_l as coefficients rather than Q_l. The word "geometric" means that algebraic cycles are taken over the algebraic closure k^_ of the base field k. The cycle-class map must be a surjection onto the classes in H^(2r)(X_(k^_),Z_l(r)) fixed by the Galois group Gal(k^_/L) for some finite extension field L/k, for every prime l distinct from the field characteristic (Brantner 2026). It is not a proof of the general conjecture.


See also

Algebraic Cycle, Hodge Conjecture, Zeta Function

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References

Brantner, L. "The Tate Conjecture for Ordinary Calabi-Yau Threefolds." 9 Oct 2026. https://arxiv.org/abs/2610.13939.Tate, J. T. "Algebraic Cycles and Poles of Zeta Functions." In Arithmetical Algebraic Geometry (Proc. Conf. Purdue Univ., 1963). New York: Harper and Row, pp. 93-110, 1965.

Cite this as:

Weisstein, Eric W. "Tate Conjecture." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/TateConjecture.html

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