标题： 关于Fitting子群和可解根的定义性的备注 显示英文标题

标题： A remark on the definability of the Fitting subgroup and the soluble radical

摘要： 设$G$为一个任意的群。 我们证明，如果$G$的Fitting子群是幂零的，则它是可定义的。 我们也证明，那些Fitting子群的幂零类最多为$n$的群的类是初等的。 我们给出一个群（任意饱和）的例子，其Fitting子群是可定义的但不是幂零的。 给出了关于可解根的类似结果。 显示英文摘要

摘要： Let $G$ be an arbitrary group. We show that if the Fitting subgroup of $G$ is nilpotent then it is definable. We show also that the class of groups whose Fitting subgroup is nilpotent of class at most $n$ is elementary. We give an example of a group (arbitrary saturated) whose Fitting subgroup is definable but not nilpotent. Similar results for the soluble radical are given.