On singular Artin monoids

Abstract

In this paper we study some combinatorial aspects of the singular Artin monoids. Firstly, we show that a singular Artin monoid $SA$ can be presented as a semidirect product of a graph monoid with its associated Artin group $A$. Such a decomposition implies that a singular Artin monoid embeds in a group. Secondly, we give a solution to the word problem for the FC type singular Artin monoids. Afterwards, we show that FC type singular Artin monoids have the FRZ property. Briefly speaking, this property says that the centralizer in $SA$ of any non-zero power of a standard singular generator $τ_s$ coincides with the centralizer of any non-zero power of the corresponding non-singular generator $σ_s$. Finally, we prove Birman's conjecture, namely, that the desingularization map $η: SA \to \Z [A]$ is injective, for right-angled singular Artin monoids.