Finitely displaced normal sub-IAPS

From Groupprops

This article defines a group sub-IAPS property: a property that can be evaluated to true/false given an IAPS of groups and a sub-IAPS.

Definition

Let (G,Φ) be an IAPS of groups and H be a sub-IAPS. We say that H is a finitely displaced normal sub-IAPS if H is both finitely displaced and normal in G.

Examples

Finite displacement via cancellation

  • In the IAPS of symmetric groups, the sub-IAPS of alternating groups is finitely displaced: we can use the homomorphism from Sn to An+2 that pads with the identity element if inside Ana and with the transposition outside An.
  • In the GL IAPS, the sub-IAPS of special linear groups is finitely displaced: any element of GL(n,R) lives inside SL(n+1,R) that pads with the inverse of the determinant.

Finite displacement via a non-concatenation method

In these examples, the finite displacement strategy does not involve concatenation.

Relation with other properties

Weaker properties

Property Meaning Proof of implication Proof of strictness (reverse implication failure) Intermediate notions
finitely displaced sub-IAPS remove the normality assumption (obvious) general linear IAPS inside general affine IAPS |FULL LIST, MORE INFO

Incomparable properties

Property Meaning Proof of non-implication Proof of non-implication (reverse) Intermediate notions
contrasaturated normal sub-IAPS every element of the IAPS can be concatenated into the sub-IAPS follows from the generic abelian example for power sub-APS of power APS may be finitely displaced (finitely displaced normal not implies contrasaturated) constant-abelian-quotient not implies finitely displaced + eventually constant-abelian-quotient implies contrasaturated
eventually constant-abelian-quotient sub-IAPS normal sub-IAPS whose quotient APS is eventually isomorphic to the constant APS for an abelian group (via contrasaturated normal) constant-abelian-quotient not implies finitely displaced