Convexité rationnelle des sous-variétés immergées lagrangiennes
We study the evolution of a closed, convex hypersurface in in direction of its normal vector, where the speed equals a power of the mean curvature. We show that if initially the ratio of the biggest and smallest principal curvatures at every point is close enough to , depending only on and , then this is maintained under the flow. As a consequence we obtain that, when rescaling appropriately as the flow contracts to a point, the evolving surfaces converge to the unit sphere.
These are the lecture notes of a minicourse given at a winter school in Marseille 2011. The aim of the course was to give an introduction to recent work on the geometry of the space of Kähler metrics associated to an ample line bundle. The emphasis of the course was the role of convexity, both as a motivating example and as a tool.
Nous étudions les conditions sous lesquelles un point d’une surface riemannienne possède un voisinage pouvant être paramétrisé par des coordonnées polaires. Le point en question peut être un point régulier ou un point singulier conique. Nous étudions aussi la régularité de ces coordonnées polaires en fonction de la régularité de la courbure.