Technion Mathematics colloquium Speaker: Mikhail Zaidenberg (University of Grenoble) Title: Flexible varieties and automorphisms groups Time: Monday, April 16, 3:30 pm Place: Amado 232, Technion Abstract: Given an affine algebraic variety X of dimension n â~I 2, we let SAut(X ) denote the special automorphism group of X i.e., the subgroup of the full automorphism group Aut(X ) generated by all one-parameter unipotent subgroups. We show that if SAut(X ) is transitive on the smooth locus Xreg of X then it is infinitely transitive on Xreg . In turn, the transitivity is equivalent to the ï¬~Bexibility of X . The latter means that for every smooth point x â~H~H Xreg the tangent space Tx X is spanned by the velocity vectors at x of one-parameter unipotent subgroups of Aut(X ). We provide different applications and examples. This is a report on a joint work with Ivan Arzhantsev, Hubert Flenner, Shulim Kaliman, Karine Kuyumzhiyan, and Frank Kutzschebauch. Colloquium Homepage: <http://www.technion.ac.il/~yehuday/colloquium/colloq.html> --------------------------------------------------------- Technion Math. Net (TECHMATH) Editor: Michael Cwikel <techm@math.technion.ac.il> Announcement from: Amir Yehudayoff <amir.yehudayoff@gmail.com>