International Journal of Group Theory (Dec 2013)
On the probability of being a 2-Engel group
Abstract
Let $G$ be a finite group and $d_2(G)$ denotes the probabilitythat $[x,y,y]=1$ for randomly chosen elements $x,y$ of $G$. Wewill obtain lower and upper bounds for $d_2(G)$ in the case wherethe sets $E_G(x)={yin G:[y,x,x]=1}$ are subgroups of $G$ forall $xin G$. Also the given examples illustrate that all thebounds are sharp.