Colliot-Thélène–Sansuc–Kato–Saito conjecture for zero-cycles

Let FF be a number field and let YY be a smooth projective geometrically connected variety over FF. Let Ω\Omega be the set of places of FF and Ωf\Omega_f the set of finite places. Denote by CH0(Y)^\widehat{\operatorname{CH}_0(Y)} and CH0,A(Y)^\widehat{\operatorname{CH}_{0,\mathbf{A}}(Y)} the relevant profinite completions of the global and adelic Chow groups of zero-cycles. The Brauer–Manin pairing gives a map from the adelic completion to Hom(Br(Y),Q/Z)\operatorname{Hom}(\operatorname{Br}(Y),\mathbb{Q}/\mathbb{Z}).

Colliot-Thélène–Sansuc–Kato–Saito conjecture. The complex

CH0(Y)^ΔCH0,A(Y)^Hom(Br(Y),Q/Z)\widehat{\operatorname{CH}_0(Y)}\stackrel{\Delta}{\longrightarrow}\widehat{\operatorname{CH}_{0,\mathbf{A}}(Y)}\longrightarrow\operatorname{Hom}(\operatorname{Br}(Y),\mathbb{Q}/\mathbb{Z})

is exact.

This asserts that the Brauer–Manin obstruction is the only obstruction to weak approximation for zero-cycles. The source attributes the conjecture to Colliot-Thélène and Sansuc for geometrically rational varieties and to Kato and Saito for general smooth projective varieties; its resolution is not specified.

Sources & referencesView supporting material

Primary source

Evangelia Gazaki and Jonathan Love, “Local and local-to-global Principles for zero-cycles on geometrically Kummer K3 surfaces”, arXiv:2402.12588 (2026).

Additional references

2 papers in this index state this conjecture (2014–2024). The statement above is taken from the most recent of them; the others are arXiv:1409.0993.

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