GENERATING INFINITE SYMMETRIC GROUPS

Abstract

Let $S={\mathop{\rm Sym}(\Omega)$ be the group of all permutations of an infinite set $\Omega$. Extending an argument of Macpherson and Neumann, it is shown that if $U$ is a generating set for $S$ as a group, then there exists a positive integer $n$ such that every element of $S$ may be written as a group word of length at most $n$ in the elements of $U$. Likewise, if $U$ is a generating set for $S$ as a monoid, then there exists a positive integer $n$ such that every element of $S$ may be written as a monoid word of length at most $n$ in the elements of $U$. Some related questions and recent results are noted, and a brief proof is given of a result of Ore's on commutators, which is used in the proof of the above result.