Finitely displaced normal sub-IAPS
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 be an IAPS of groups and be a sub-IAPS. We say that is a finitely displaced normal sub-IAPS if is both finitely displaced and normal in .
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 to that pads with the identity element if inside a and with the transposition outside .
- In the GL IAPS, the sub-IAPS of special linear groups is finitely displaced: any element of lives inside 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.
- Power sub-APS of power APS may be finitely displaced uses the fact that infinity can absorb anything finite to demonstrate finite displacement.
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 |