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Birational diffeomorphisms of the sphere of order 2

Le : 07/02/2014 14h00
Par : Maria Robayo (Bâle)
Lieu : I 001
Lien web :
Résumé : Let S be the real algebraic projective surface defined by the equation w2 = x2+y2+z2 in P3_R. The group of birational diffeomorphisms of S is denoted by Diffbir(S) and corresponds to those birational transformations f such that f and f ^{-1} are defined at every real point of S. For g in Diffbir(S) of finite order it is known that if (X,g') is the minimal resolution of (S,g'), where g’ in Aut(X) is the lift of g, then (1) rank Pic(X)^g'=1 and X is a Del Pezzo surface, or (2) rank Pic(X)^g'=2 and X→ P1 is a conic bundle. We present some algebraic and geometric results about the conjugacy classes of birational diffeomorphisms of finite order for the case (2).