Inner holomorph of a group

Definition

Let $G$ be a group. The inner holomorph of $G$ can be defined as the semidirect product $G\rtimes \operatorname {Inn} (G)$ where $\operatorname {Inn} (G)$ is the inner automorphism group with the usual action.

It is a subgroup of the holomorph $G\rtimes \operatorname {Aut} (G)$ and is a quotient of the direct product $G\times G$.

Facts

When $G$ is an group having an automorphism whose restriction to the center is the inverse map, this is isomorphic to the central product of two copies of $G$ with the center $Z(G)$ of both copies identified: $G*_{Z(G)}G$.

If $G$ is a group whose center is a direct factor, this group is isomorphic to the direct product of $G$ and $\operatorname {Inn} (G)$.