On Equality of Certain Automorphism Groups

Abstract: Let $G = H\times A$ be a group, where $H$ is a purely non-abelian subgroup of $G$ and $A$ is a non-trivial abelian factor of $G$. Then, for $n \geq 2$, we show that there exists an isomorphism $\phi : Aut_{Z(G)}^{\gamma_{n}(G)}(G) \rightarrow Aut_{Z(H)}^{\gamma_{n}(H)}(H)$ such that $\phi(Aut_{c}^{n-1}(G))=Aut_{c}^{n-1}(H)$. Also, for a finite non-abelian $p$-group $G$ satisfying a certain natural hypothesis, we give some necessary and sufficient conditions for $Autcent(G) = Aut_c^{n-1}(G)$. Furthermore, for a finite non-abelian $p$-group $G$ we study the equality of $Autcent(G)$ with $Aut_{Z(G)}^{\gamma_{n}(G)}(G)$.