2020/09/30 by Charles Vial, Vial, Charles
Mathematics · #14C15 #14C25 #14E05 #14J42 #14K99 #Algebraic Geometry (math.AG) #FOS: Mathematics #math.AG #msc:14C15 #msc:14C25 #msc:14E05 #msc:14J42 #msc:14K99
paper · pdf · doi:10.48550/arxiv.2010.00099
v3: introduction improved thanks to the referee's suggestions; new results of Li-Zhang arXiv:2201.00493 added
arxiv created 2022/03/17 · arxiv updated 2022/03/18
We introduce a new ascending filtration, that we call the co-radical filtration in analogy with the basic theory of co-algebras, on the Chow groups of pointed smooth projective varieties. In the case of zero-cycles on projective hyper-Kähler manifolds, we conjecture it agrees with a filtration introduced by Voisin. This is established for moduli spaces of stable objects on K3 surfaces, for generalized Kummer varieties and for the Fano variety of lines on a smooth cubic fourfold. Our overall strategy is to view the birational motive of a smooth projective variety as a co-algebra object with respect to the diagonal embedding and to show in the aforementioned cases the existence of a so-called strict grading whose associated filtration agrees with the filtration of Voisin. As results of independent interest, we upgrade to rational equivalence Voisin's notion of "surface decomposition" and show that the birational motive of some projective hyper-Kähler manifolds is determined, as a co-algebra object, by the birational motive of a surface. We also relate our co-radical filtration on the Chow groups of abelian varieties to Beauville's eigenspace decomposition.