Chow–Künneth decomposition conjecture

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

ΔX=j=02dΔj,XH2d(X×X).\Delta_X=\sum_{j=0}^{2d}\Delta_{j,X}\in H^{2d}(X\times X).

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

πj,X2=πj,X,πj,Xπj,X=0for jj,\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.

Sources & referencesView supporting material

Primary source

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

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