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locally nilpotent group (Definition)

Definition

A locally nilpotent group is a group in which every finitely generated subgroup is nilpotent.

Examples

All nilpotent groups are locally nilpotent, because subgroups of nilpotent groups are nilpotent.

An example of a locally nilpotent group that is not nilpotent is $ \Dih (\mathbb{Z}(2^\infty))$, the generalized dihedral group formed from the quasicyclic $ 2$-group $ \mathbb{Z}(2^\infty)$.

The Fitting subgroup of any group is locally nilpotent.

All N-groups are locally nilpotent. More generally, all Gruenberg groups are locally nilpotent.

Properties

Any subgroup or quotient of a locally nilpotent group is locally nilpotent. Restricted direct products of locally nilpotent groups are locally nilpotent.

For each prime $ p$, the elements of $ p$-power order in a locally nilpotent group form a fully invariant subgroup (the maximal $ p$-subgroup). The elements of finite order in a locally nilpotent group also form a fully invariant subgroup (the torsion subgroup), which is the restricted direct product of the maximal $ p$-subgroups. (This generalizes the fact that a finite nilpotent group is the direct product of its Sylow subgroups.)

Every group $ G$ has a unique maximal locally nilpotent normal subgroup. This subgroup is called the Hirsch-Plotkin radical, or locally nilpotent radical, and is often denoted $ \HP (G)$. If $ G$ is finite (or, more generally, satisfies the maximal condition), then the Hirsch-Plotkin radical is the same as the Fitting subgroup, and is nilpotent.



"locally nilpotent group" is owned by yark.
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See Also: locally $\cal P$, nilpotent group, normalizer condition

Also defines:  locally nilpotent, Hirsch-Plotkin radical, locally nilpotent radical
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Cross-references: maximal condition, normal subgroup, Sylow subgroups, direct product, finite nilpotent group, torsion subgroup, maximal, fully invariant subgroup, order, prime, restricted direct products, Gruenberg groups, N-groups, Fitting subgroup, quasicyclic, generalized dihedral group, subgroups, nilpotent groups, nilpotent, finitely generated subgroup, group
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This is version 4 of locally nilpotent group, born on 2006-02-14, modified 2007-06-13.
Object id is 7619, canonical name is LocallyNilpotentGroup.
Accessed 2852 times total.

Classification:
AMS MSC20F19 (Group theory and generalizations :: Special aspects of infinite or finite groups :: Generalizations of solvable and nilpotent groups)

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