Tel Aviv University Colloquium Hello everyone, The next colloquium talk will be held on Monday, 7/3/2011, 12:15, Schreiber 006, Tel Aviv University. The speaker is Sergei Tabachnikov (Pennsylvania State University) and the title of his talk is Geometry, algebra, and dynamics of the pentagram map The abstract is given below. Tea and coffee at 12:00, same room. Hope to see you there. For information about future colloquiua, see <http://www.math.tau.ac.il/~klartagb/colloq_2010.html> You are all welcome to suggest colloquium speakers, especially for the next academic year. Yours, Bo'az ------------------------- Abstract: Introduced by R. Schwartz almost 20 years ago, the pentagram map acts on plane n-gons, considered up to projective equivalence, by drawing the diagonals that connect second-nearest vertices and taking the new n-gon formed by their intersections. I shall survey recent work on the pentagram map, in particular, I shall demonstrate that the dynamics of the pentagram map is very regular: the map is completely integrable. I shall show that the pentagram map is a discretization of the Boussinesq equation, a well known completely integrable partial differential equation. An unexpected relation between the spaces of polygons and combinatorial objects called the 2-frieze patterns (generalizing the frieze patterns of Coxeter) will be revealed. Eight new configuration theorems of projective geometry will be demonstrated. The talk will be illustrated by computer animation. --------------------------------------------------------- Technion Math Net-2 (TECHMATH2) Editor: Michael Cwikel <techm@math.technion.ac.il> Announcement from: Bo'az Klartag <klartagb@post.tau.ac.il>