Colliot-Thélène–Kahn conjecture on unramified cohomology of uniruled threefolds

Let F\mathbb{F} be the finite field under consideration, let \ell be a prime, and let XX be a smooth projective geometrically uniruled F\mathbb{F}-variety of dimension 33. The group Hnr3(X,Q/Z(2))H^{3}_{\operatorname{nr}}(X,\mathbb{Q}_{\ell}/\mathbb{Z}_{\ell}(2)) is the third unramified cohomology group of XX with these coefficients. Colliot-Thélène–Kahn conjecture. For every such XX,

Hnr3(X,Q/Z(2))=0.H^{3}_{\operatorname{nr}}(X,\mathbb{Q}_{\ell}/\mathbb{Z}_{\ell}(2))=0.

This predicts the vanishing of a stable birational invariant for geometrically uniruled threefolds over finite fields and is presented as a conjecture of Colliot-Thélène and Kahn; its resolution status is not specified in the supplied text.

Sources & referencesView supporting material

Primary source

Federico Scavia and Fumiaki Suzuki, “Two coniveau filtrations and algebraic equivalence over finite fields”, arXiv:2304.08560 (2024).

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