Coloured knots and permutations representing 3-manifolds.
On définit le bicomplexe , extension naturelle du complexe engendré par un ensemble simplicial . Ceci permet de définir la notion de ruban de base un cycle de . La somme directe de l’homologie des colonnes de contient, outre l’homologie de , des groupes dans lesquels se trouvent les obstructions à l’existence de rubans. Si est un sous-ensemble simplicial, stable par subdivision, de l’ensemble des simplexes singuliers d’un espace topologique, l’existence de rubans entraîne l’invariance...
We give a characterization of the geometric automorphisms in a certain class of (not necessarily irreducible) free group automorphisms. When the automorphism is geometric, then it is induced by a pseudo-Anosov homeomorphism without interior singularities. An outer free group automorphism is given by a -cocycle of a -complex (a standard dynamical branched surface, see [7] and [9]) the fundamental group of which is the mapping-torus group of the automorphism. A combinatorial construction elucidates...
François Jaeger found a number of beautiful connections between combinatorics and the topology of knots and links, culminating in an intricate relationship between link invariants and the Bose-Mesner algebra of an association scheme. This paper gives an introduction to this connection.