On signatures and a subgroup of a central extension to the mapping class group.
On the complexity of braids
We define a measure of “complexity” of a braid which is natural with respect to both an algebraic and a geometric point of view. Algebraically, we modify the standard notion of the length of a braid by introducing generators , which are Garside-like half-twists involving strings through , and by counting powered generators as instead of simply . The geometrical complexity is some natural measure of the amount of distortion of the times punctured disk caused by a homeomorphism. Our main...
On the Configuration Spaces of Grassmannian Manifolds
Let be the -th ordered configuration space of all distinct points in the Grassmannian of -dimensional subspaces of , whose sum is a subspace of dimension . We prove that is (when non empty) a complex submanifold of of dimension and its fundamental group is trivial if , and and equal to the braid group of the sphere
On the dynamics of (left) orderable groups
We develop dynamical methods for studying left-orderable groups as well as the spaces of orderings associated to them. We give new and elementary proofs of theorems by Linnell (if a left-orderable group has infinitely many orderings, then it has uncountably many) and McCleary (the space of orderings of the free group is a Cantor set). We show that this last result also holds for countable torsion-free nilpotent groups which are not rank-one Abelian. Finally, we apply our methods to the case of braid...
On the inverse braid and reflection monoids of type .
On the Jones polynomial of closed 3-braids.
On the representation theory of braid groups
This work presents an approach towards the representation theory of the braid groups . We focus on finite-dimensional representations over the field of Laurent series which can be obtained from representations of infinitesimal braids, with the help of Drinfeld associators. We set a dictionary between representation-theoretic properties of these two structures, and tools to describe the representations thus obtained. We give an explanation for the frequent apparition of unitary structures on classical...
On the residual properties of link groups.
On the structure of the centralizer of a braid
On Tits' conjecture and other questions concerning Artin and generalized Artin groups.
Parametrized braid groups of Chevalley groups.
PBW-bases of quantum groups.
Presentations for the punctured mapping class groups in terms of Artin groups.
Presentations of surface braid groups by graphs
We extend and generalise Sergiescu's results on planar graphs and presentations for the braid group Bₙ to other topological generalisations of Bₙ.
Pure braid subgroups of braided Thompson's groups.
Pure virtual braids homotopic to the identity braid
Two virtual link diagrams are homotopic if one may be transformed into the other by a sequence of virtual Reidemeister moves, classical Reidemeister moves, and self crossing changes. We recall the pure virtual braid group. We then describe the set of pure virtual braids that are homotopic to the identity braid.
Quotients infinitésimaux du groupe de tresses
Nous définissons et entamons l’étude d’analogues infinitésimaux des quotients principaux (algèbres de Temperley-Lieb, Hecke, Birman-Wenzl-Murakami) de l’algèbre de groupe du groupe d’Artin . Ce sont des algèbres de Hopf qui correspondent à des groupes réductifs, et permettent de donner un cadre général aux représentations dérivées des représentations classiques de . Nous décomposons complètement l’algèbre de Temperley-Lieb infinitésimale, et en déduisons plusieurs résultats d’irréductibilité.
Relations among the squares of the generators of the braid groups.
Rings of Fricke Characters and Automorphism Groups of Free Groups.
Salvetti complex, spectral sequences and cohomology of Artin groups
The aim of this short survey is to give a quick introduction to the Salvetti complex as a tool for the study of the cohomology of Artin groups. In particular we show how a spectral sequence induced by a filtration on the complex provides a very natural and useful method to study recursively the cohomology of Artin groups, simplifying many computations. In the last section some examples of applications are presented.