Reconstructing a Graph from the Incidence Relation on its Edge Set
The intersection matrix of a simplicial complex has entries equal to the rank of the intersecction of its facets. We prove that this matrix is enough to define up to isomorphism a triangulation of a surface.
On établit une récurrence du 6-ième ordre pour le nombre de recouvrements d'un rectangle de largeur 3 et de longueur n à l'aide de «triminos». Des problèmes analogues peuvent se poser à propos de découpages électoraux.
We solve the last missing case of a “two delegation negotiation” version of the Oberwolfach problem, which can be stated as follows. Suppose we have two negotiating delegations with n=mk members each and we have a seating arrangement such that every day the negotiators sit at m tables with k people of the same delegation at one side of each table. Every person can effectively communicate just with three nearest persons across the table. Our goal is to guarantee that over the course of several days,...