A generalization of a question asked by B. H. Neumann

英文摘要：

Let $w \in F_2$ be a word and let $m$ and $n$ be two positive integers. We say that a finite group $G$ has the $w_{m,n}$-property if however a set $M$ of $m$ elements and a set $N$ of $n$ elements of the group is chosen, there exist at least one element of $x \in M$ and at least one element of $y \in M$ such that $w(x,y)=1.$ Assume that there exists a constant $γ< 1$ such that whenever $w$ is not an identity in a finite group $X$, then the probability that $w(x_1,x_2)=1$ in $X$ is at most $γ.$ If $m\leq n$ and $G$ satisfies the $w_{m,n}$-property, then either $w$ is an identity in $G$ or $|G|$ is bounded in terms of $γ, m$ and $n$. We apply this result to the 2-Engel word.