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March 08, 2010
Monday, March 08
Geometry and Topology
Time: 15:30
Speaker: Gereon Quick (Muenster)
Title: "Torsion algebraic cycles and étale cobordism"
Room: MC 108

Abstract: We show that the classical integral cycle class map from algebraic cycles to étale cohomology factors through a quotient of l-adic étale cobordism over an algebraically closed field of positive characteristic. This implies that there is a strong topological obstruction for cohomology classes to be algebraic and that examples of Atiyah and Hirzebruch for non-algebraic integral cohomology classes and of Totaro for non-trivial elements in the Griffiths group also work in positive characteristic.