Groups, Geometry, and Dynamics

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Volume 1, Issue 2, 2007, pp. 111–133
DOI: 10.4171/GGD/7

Published online: 2007-06-30

Représentation par des transvections des groupes d'Artin–Tits

Eddy Godelle[1]

(1) Université de Caen, France

In a recent article, C. Kassel and C. Reutenauer studied the connection between the 4 strand braid group and Sturmian morphisms in word combinatorics. The aim of the current work is to extend this approach into a general connection between braid groups (of any index) and episturmian morphisms, a natural generalization of sturmian morphisms. Our key tool consists in associating with every graph a certain finite family of automorphisms of a free group. In the case of a complete graph, we recover some well-known family of episturmian morphisms. Now, considering the path of length n, we deduce a seemingly new representation of the braid group Bn +1 in Aut(Fn). By considering some other graphs, we similarly obtain representations of various Artin–Tits groups, in particular some affine braid groups. Our representation is faithful for B3 and B4; for other cases, the question of faithfulness remains open.

Keywords: Representation of braid groups, automorphisms of free groups, episturmian morphisms

Godelle Eddy: Représentation par des transvections des groupes d'Artin–Tits. Groups Geom. Dyn. 1 (2007), 111-133. doi: 10.4171/GGD/7