Chow–Künneth decomposition conjecture

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Let kk be an algebraically closed field, let XX be a smooth projective variety of dimension dd over kk, and let H∗H^* be a Weil cohomology. Write the Künneth decomposition of the diagonal as

ΔX=∑j=02dΔj,X∈H2d(X×X).\Delta_X=\sum_{j=0}^{2d}\Delta_{j,X}\in H^{2d}(X\times X).

Chow–Künneth conjecture. There exist correspondences πj,X∈CHd(X×X)\pi_{j,X}\in CH^d(X\times X) satisfying

πj,X2=πj,X,πj,X∘πj′,X=0for j≠j′,\pi_{j,X}^2=\pi_{j,X},\qquad \pi_{j,X}\circ\pi_{j',X}=0\quad\text{for }j\ne j', ∑jπj,X=ΔX,\sum_j\pi_{j,X}=\Delta_X,

and cl(πj,X)=Δj,Xcl(\pi_{j,X})=\Delta_{j,X} for any choice of Weil cohomology.

Such algebraic mutually orthogonal idempotent lifts of the Künneth components would give a motivic decomposition of XX and strengthen Grothendieck's standard conjecture that the Künneth components are algebraic. The source does not state whether this stronger conjecture is resolved.

References

Primary source

Humberto A. Diaz, “The motive of a smooth Theta divisor”, arXiv:1603.04345 (2016).

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