The absolute Frattini automorphisms

Abstract

Let G be a finite non-abelian p-group, where p is a prime number, and Aut(G) be the group of all automorphisms of $G$. An automorphism alpha of $G$ is called absolute central automorphism if, x^{-1}alpha(x) lies in L(G), where L(G) is the absolute center of G. In addition, alpha is an absolute Frattini automorphism if x^{-1}alpha(x) is in Phi(L(G)), where Phi(L(G)) is the Frattini subgroup of the absolute center of G, and let LF(G) denote the group of all such automorphisms of G. Also, we denote by C_{LF(G)}(Z(G)) and C_{LA(G)}(Z(G)), respectively, the group of all absolute Frattini automorphisms and the group of all absolute central automorphisms of G, fixing elementwise the center Z(G) of G . We give necessary and sufficient conditions on a finite non-abelian p-group G of class two such that C_{LF(G)}(Z(G))=C_{LA(G)}(Z(G)). Moreover, we investigate the conditions under which LF(G) is a torsion-free abelian group.