Aller au contenu  Aller au menu  Aller à la recherche

Bienvenue - Laboratoire Jacques-Louis Lions

Print this page |

Chiffres-clé

Chiffres clefs

189 personnes travaillent au LJLL

86 permanents

80 chercheurs et enseignants-chercheurs permanents

6 ingénieurs, techniciens et personnels administratifs

103 personnels non permanents

74 doctorants

15 post-doc et ATER

14 émérites et collaborateurs bénévoles

 

Chiffres janvier 2022

 

Séminaire du LJLL - 24 02 2017 14h00 : J. Llibre

Jaume Llibre (Université Autonome de Barcelone)
The center-focus problem, the integrability of the centers, and the divergence

Abstract
We shall recall briefly how can be the local phase portraits of the equilibrium points of an analytic differential system in the plane, and we shall put our attention in the center-focus problem, i.e. how to distinguish a center from a focus. This is a difficult problem which is not completely solved. We shall provide some new results about the local integrability of the centers and on the problem of distinguishing one focus from a center using the divergence of the differential system.