Groupes de Garside

Abstract

Define a Garside monoid to be a cancellative monoid where right and left lcm's exist and that satisfy additional finiteness assumptions, and a Garside group to be the group of fractions of a Garside monoid. The family of Garside groups contains the braid groups, all spherical Artin-Tits groups, and various generalizations previously considered. 2 2 In particular, the Garside groups considered in [17] are special cases of those considered here; the latter had been called “small Gaussian” in earlier works; the name has been changed in order to uniformize the terminology with works by Bessis, Charney, Digne, Michel, and other authors. Here we prove that Garside groups are biautomatic, and that being a Garside group is a recursively enumerable property, i.e., there exists an algorithm constructing the (infinite) list of all small Gaussian groups. The latter result relies on an effective, tractable method for recognizing those presentations that define a Garside monoid.