Gérard Besson's Blog

Lecture by Luc Lemaire

Gérard Besson — Tue, 16 Feb 2010 07:05:26 +0000

Professor Luc Lemaire from the Université Libre de Bruxelles gave a talk (in french) on the proof of the Poincaré conjecture for a large audience (high school students, teachers, etc…). The text of his lecture is available here.

Post-Doctoral Positions

Gérard Besson — Sat, 06 Feb 2010 09:00:22 +0000

The A.N.R. Grant named FOG (Flots et opérateurs géométriques) opens three six months post-doctoral positions in one of the partner departments to be held during the academic year 2010-2011. The applicants should be working on a subject related to the grant theme. The deadline for applications is May 1st and more informations are available here.

Bourbaki goes to Luxembourg (garden)

Gérard Besson — Sat, 09 Jan 2010 08:31:13 +0000

On march 15th, 2009, I gave the Bourbaki lecture on “the differentiable sphere theorem”. As a protest against the government policy, the beginning of the lecture has been given on the bandstand of Jardin du Luxembourg. After ten minutes we had to leave when the senate police arrived. We then finished the lecture in the regular room at Institut Henri Poincaré. A video is posted on You Tube.

The power of mathematics, why they still are unavoidable

Gérard Besson — Fri, 01 Jan 2010 16:19:13 +0000

The magazine La Recherche recently published a special issue (Les Dossiers de La Recherche n°37 trimestriel novembre 2009). An improved version of a previous paper appeared in this volume. It is entitled “Comment on est venu à bout de la conjecture de Poincaré” and contains a wide-audience description of Perelman’s works on Hamilton’s Ricci flow leading to the proof of Poincaré’s Conjecture. A previous version also published in La Recherche is available here.

Collapsing irreducible 3-manifolds with nontrivial fundamental group

Gérard Besson — Fri, 25 Dec 2009 17:38:55 +0000

This is a joint work with Laurent Bessières, Michel Boileau, Sylvain Maillot and Joan Porti. Let M be a closed, orientable, irreducible, non-simply connected 3-manifold.We prove that if M admits a sequence of Riemannian metrics which volume-collapses and whose sectional curvature is locally controlled, then M is a graph manifold. This is the last step in Perelman’s proof of Thurston’s Geometrisation Conjecture.

The reference is:

L. Bessières, G. Besson, M. Boileau, S. Maillot and J. Porti Collapsing irreducible 3-manifolds with nontrivial fundamental group Invent math (2010) 179: 435–460.

Sciences Festival in Paris

Gérard Besson — Fri, 25 Dec 2009 16:02:31 +0000

For the Sciences Festival in Paris, I gave a lecture in Jussieu on Saturday, November 21st. The title was “La conjecture (résolue) de Poincaré : flots géométriques et applications”. I described the curve shortening process and its application to images denoising. After a description of the classification of orientable and closed surfaces, I stated the Poincaré conjecture. I then attempted an intuitive definition of the Ricci curvature and alluded to Hamilton’s Ricci flow.

Find here the lecture Beamer file.