On subgroups of free Burnside groups of large odd exponent

Abstract

We prove that every noncyclic subgroup of a free $m$-generator Burnside group $B(m,n)$ of odd exponent $n \gg 1$ contains a subgroup $H$ isomorphic to a free Burnside group $B(\infty,n)$ of exponent $n$ and countably infinite rank such that, for every normal subgroup $K$ of $H$, the normal closure $\langle K \rangle^{B(m,n)}$ of $K$ in $B(m,n)$ meets $H$ in $K$. This implies that every noncyclic subgroup of $B(m,n)$ is $\operatorname{SQ}$-universal in the class of groups of exponent $n$.