ACIC implies nilpotent (finite groups)

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This article gives the statement and possibly, proof, of an implication relation between two group properties. That is, it states that every group satisfying the first group property must also satisfy the second group property
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Property-theoretic statement

For finite groups, the property of being ACIC is stronger than the property of being nilpotent.

Verbal statement

Any finite ACIC-group is nilpotent.

Definitions used

Automorph-conjugate subgroup

Further information: automorph-conjugate subgroup

A subgroup H of a group G is termed an automorph-conjugate subgroup if for every automorphism \sigma of G, H and \sigma(H) are conjugate subgroups.


Further information: ACIC-group

A group is termed ACIC if every automorph-conjugate subgroup is characteristic, or equivalently, any automorph-conjugate subgroup is normal.

Finite nilpotent group

Further information: Finite nilpotent group

A finite group is termed nilpotent if all Sylow subgroups are normal (this is just one of the formulations of nilpotence for finite groups). The definition breaks down for infinite groups).

Facts used

Related facts


Proof using subgroup property collapse

For any finite group, we have:

Sylow \implies automorph-conjugate

And for an ACIC-group, we have:

Automorph-conjugate \implies normal

Thus, for a finite ACIC-group, we have:

Sylow \implies Normal

Which is precisely the condition for being a finite nilpotent group.