Normal fully normalized subgroup

This page describes a subgroup property obtained as a conjunction (AND) of two (or more) more fundamental subgroup properties: normal subgroup and fully normalized subgroup
View other subgroup property conjunctions | view all subgroup properties

Definition

Symbol-free definition

A subgroup of a group is termed normal fully normalized if it is normal in the whole group, and every automorphism of the subgroup extends to an inner automorphism of the whole group.

Definition with symbols

A subgroup $H$ of a group $G$ is termed normal fully normalized if $H$ is normal in $G$, and every $\sigma \in \operatorname{Aut}(H)$ can be realized as conjugation by $g$ for some $g \in G$.

Equivalently, $H$ is normal in $G$, and the natural map $G \to \operatorname{Aut}(H)$ is surjective.

Metaproperties

Left realization

Every group can be realized as a normal fully normalized subgroup in some group, for instance, in its holomorph. Further information: Every group is normal fully normalized in its holomorph