Knot and braid invariants from contact homology. I.
Knot and braid invariants from contact homology. II.
Krammer's representation of the pure braid group .
Le groupe d'automorphismes du groupe modulaire
Le but de cet article est de donner une autre démonstration plus simple du théorème d’Ivanov (Théorème 1) qui assure que le groupe de toutes les difféotopies d’une surface orientable et fermée de genre est complet. En étudiant l’action d’un automorphisme quelconque du groupe sur les difféotopies d’ordre fini, on montre que les involutions hyperelliptiques sont globalement préservées. Le théorème d’Ivanov est alors une conséquence d’un résultat de Dyer et Grossmann qui affirm que le groupe...
Left-Garside categories, self-distributivity, and braids
In connection with the emerging theory of Garside categories, we develop the notions of a left-Garside category and of a locally left-Garside monoid. In this framework, the relationship between the self-distributivity law LD and braids amounts to the result that a certain category associated with LD is a left-Garside category, which projects onto the standard Garside category of braids. This approach leads to a realistic program for establishing the Embedding Conjecture of [Dehornoy, Braids and...
Lifting of homeomorphisms to branched coverings of a disk
We consider a simple, possibly disconnected, d-sheeted branched covering π of a closed 2-dimensional disk D by a surface X. The isotopy classes of homeomorphisms of D which are pointwise fixed on the boundary of D and permute the branch values, form the braid group Bₙ, where n is the number of branch values. Some of these homeomorphisms can be lifted to homeomorphisms of X which fix pointwise the fiber over the base point. They form a subgroup of finite index in Bₙ. For each equivalence class...
Linear representations of the group of conjugating automorphisms and the braid groups of some manifolds.
L'ordre de Dehornoy sur les tresses
Markov traces and knot invariants related to Iwahori-Hecke algebras of type B.
Minimal length coset representatives for quotients of parabolic subgroups in Coxeter groups
In questo lavoro viene trovata un'espressione esplicita per i rappresentanti dei laterali di sottogrupi parabolici di gruppi di Coxeter aventi lunghezza minima: dato un sistema di Coxeter ed un suo sottogruppo parabolico , con , si determina esplicitamente in ogni laterale di un elemento avente lunghezza minima. Nella sezione 2 trattiamo i casi classici, i.e. , e . Dopo ciò, nella sezione 3, diamo una procedura per risolvere il problema nei restanti casi eccezionali, insieme a qualche...
Motion of links in the 3-sphere.
New adventures in the land of -analogues (Yang-Baxter equations). (Nouvelles aventures au pays des -analogues (équation de Yang-Baxter).)
Noncommutative independence in the infinite braid and symmetric group
This is an introductory paper about our recent merge of a noncommutative de Finetti type result with representations of the infinite braid and symmetric group which allows us to derive factorization properties from symmetries. We explain some of the main ideas of this approach and work out a constructive procedure to use in applications. Finally we illustrate the method by applying it to the theory of group characters.
Non-positively curved aspects of Artin groups of finite type.
Non-standard automorphisms of branched coverings of a disk and a sphere
Let Y be a closed 2-dimensional disk or a 2-sphere. We consider a simple, d-sheeted branched covering π: X → Y. We fix a base point A₀ in Y (A₀ ∈ ∂Y if Y is a disk). We consider the homeomorphisms h of Y which fix ∂Y pointwise and lift to homeomorphisms ϕ of X-the automorphisms of π. We prove that if Y is a sphere then every such ϕ is isotopic by a fiber-preserving isotopy to an automorphism which fixes the fiber pointwise. If Y is a disk, we describe explicitly a small set of automorphisms of...
Normal all pseudo-Anosov subgroups of mapping class groups.
Numerical invariants of exponential groups and locally free approximation of the braid group.
On Galois covers of Hirzebruch surfaces.
On generalized homology of Artin groups.
On representation varieties of Artin groups, projective arrangements and the fundamental groups of smooth complex algebraic varieties