Résumé : We will discuss ribbon graphs and their topological polynomial invariant that generalizes the famous Tutte polynomial and that is called the Bollobas-Riordan (BR) polynomial. After giving the definition of ribbon graphs and discussing their correspondence with signed rotation systems, we will inspect the main topological properties of ribbon graphs seen as surfaces with boundaries. We will then introduce the BR topological polynomial invariant that satisfies a contraction-deletion recursion relation in a similar way of the Tutte polynomial. If the time allows it, we may give a glimpse of the proof of the universality theorem for the BR polynomial.
Dernière modification : Tuesday 10 March 2020 | Contact : Cyril.Banderier at lipn.univ-paris13.fr |