仿射型线群的二元表示$\tilde A$
Présentations duales des groupes de tresses de type affine $\tilde A$
摘要：
本文定义了所有Artin-Tits群的对偶幺半群，并证明了对于$\tilde A_n$型，我们得到了一个（拟）-Garside结构.这样的结构提供了标准形式的阿廷-山茨群元素，并允许解决一些问题，如确定的中心化的权力的Coxeter元素在阿廷-山茨群。更准确地说，如果$W$是Coxeter群，则可以考虑$W$上的长度$l_R$相对于由所有反射组成的生成集$R$。令$c$是$W$中的Coxeter元素，并且令$P_c$是元素$p\in W$的集合，使得$c$可以被写为具有$l_R(c)=l_R(p)+l_R(p')$的$c=pp'$。我们定义幺半群$M(P_c)$为一对一对应的集合$\underline P_c$生成的幺半群，$p\mapsto \underline p$，当$p$，$p'$和$pp'$在$P_c$和$l_R(pp')=l_R(p)+l_R(p')$中时，$P_c$只与$\underline{pp'}=\underline p.\underline p'$有关系。我们推测，$M(P_c)$的子群是与$W$相关的Artin-Tits群，它有一个简单的表示（见\ref{conjecture}（ii））。已知这些定理对于球面型Artin-Tits群是成立的。在这里，我们证明他们的阿廷-山茨群类型$\tilde A$。此外，我们表明，正是一个选择的Coxeter元素（图自同构），我们得到一个（准）Garside幺半群。证明利用了环形中的非交叉路径，这是$A$类型中使用的非交叉分区的对应物。
英文摘要：
In the present paper we define dual monoids for all Artin-Tits groups and we prove that for the type $\tilde A_n$ we get a (quasi)-Garside structure. Such a structure provides normal forms for the Artin-Tits group elements and allows to solve some questions such as to determine the centralizer of a power of the Coxeter element in the Artin-Tits group. More precisely, if $W$ is a Coxeter group, one can consider the length $l_R$ on $W$ with respect to the generating set $R$ consisting of all reflections. Let $c$ be a Coxeter element in $W$ and let $P_c$ be the set of elements $p\in W$ such that $c$ can be written $c=pp'$ with $l_R(c)=l_R(p)+l_R(p')$. We define the monoid $M(P_c)$ to be the monoid generated by a set $\underline P_c$ in one-to-one correspondence, $p\mapsto \underline p$, with $P_c$ with only relations $\underline{pp'}=\underline p.\underline p'$ whenever $p$, $p'$ and $pp'$ are in $P_c$ and $l_R(pp')=l_R(p)+l_R(p')$. We conjecture that the group of quotients of $M(P_c)$ is the Artin-Tits group associated to $W$ and that it has a simple presentation (see \ref{conjecture} (ii)). These conjectures are known to be true for spherical type Artin-Tits groups. Here we prove them for Artin-Tits groups of type $\tilde A$. Moreover, we show that for exactly one choice of the Coxeter element (up to diagram automorphism) we obtain a (quasi-) Garside monoid. The proof makes use of non-crossing paths in an annulus which are the counterpart in this context of the non-crossing partitions used for type $A$.
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