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Séminaire Géométries ICJ

On the Lüroth problem for real varieties

by Olivier Wittenberg

vendredi 27 avril 2018 de au (Europe/Paris)
at ICJ ( Fokko du Cloux )
1er étage bâtiment Braconnier, Université Claude Bernard Lyon 1 - La Doua
 Description (Joint work with Olivier Benoist.) The Lüroth problem asks whether unirational varieties are rational. It has a positive answer for complex curves and surfaces; negative answers for complex threefolds have been understood since the 70's. I will discuss the Lüroth problem for real algebraic varieties that are geometrically rational and explain a counterexample not accounted for by the topology of the real locus or by a nontrivial unramified cohomology group over the reals.