Claire Voisin

Centre national de la recherche scientifique; Distinguished Visiting Professor, School of Mathematics

November 12, 2014

We discuss the universal triviality of the \(\mathrm{CH}_0\)-group of cubic hypersurfaces, or equivalently the existence of a Chow-theoretic decomposition of their diagonal. The motivation is the study of stable irrationality for these varieties. Our main result is that this decomposition exists if and only if it exists on the cohomological level. As an application, we find that a cubic threefold has universally trivial \(\mathrm{CH}_0\) group if and only if the minimal class \(\theta^4/4!\) of its intermediate jacobian is the class of a 1-cycle (only twice this class is known to be algebraic).