Universally defined cycles

Princeton University Mathematics Department Colloquium
Topic:Universally defined cycles
Speaker:Claire Voisin
Affiliation:Centre national de la recherche scientifique; Distinguished Visiting Professor, School of Mathematics
Date:Wednesday, April 15
Time/Room:4:30pm - 5:30pm/Fine 314, Princeton University

The Franchetta conjecture (now a theorem) says basically that any line bundle on the universal family of curves of genus at least 2 restricts to a multiple of the canonical bundle on each fiber. We formulate a generalization of this statement for surfaces and provide a characterization of the Chern classes: polynomials in the Chern classes are the only "universally defined" cycles.