Real singular Del Pezzo surfaces and rationally connected threefolds

Real singular Del Pezzo surfaces and rationally connected threefolds

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Frédéric Mangolte, Université de Savoie
Fine Hall 322

Recent results on classification of real algebraic threefolds will be described. Let W -> X be a real smooth projective threefold fibred by rational curves. J. Kollár proved that if the set of real points W(R) is orientable, then a connected component N of W(R) is essentially either a Seifert fibred manifold or a connected sum of lens spaces. We proved sharp estimates on the number and the multiplicities of the Seifert fibres and on the number and the torsions of the lens spaces whenever X is a geometrically rational surface. These results answer in the affirmative three questions of Kollár. They are derived from a careful study of real singular Del Pezzo surfaces with only Du Val singularities. This is joint work with F. Catanese.