Bound-word subgroup

From Groupprops

BEWARE! This term is nonstandard and is being used locally within the wiki. [SHOW MORE]

This article defines a subgroup property: a property that can be evaluated to true/false given a group and a subgroup thereof, invariant under subgroup equivalence. View a complete list of subgroup properties[SHOW MORE]

Definition

Definition with symbols

A quantified word-letter pair is a word with a distinguished letter, with a sequence of (possibly nested) existential and universal quantifiers on all the other letters. An element in a group satisfies this pair if setting the distinguished letter equal to , the nested expression is true in the group (where existential and universal quantifiers are interpreted over ). The subgroup corresponding to a quantified word-letter pair is defined as the subgroup generated by all elements of the group satisfying that pair.

A bound-word subgroup is a possibly arbitrary join of finite intersections of subgroups corresponding to quantified word-letter pairs.

Relation with other properties

Stronger properties

Property Meaning Proof of implication Proof of strictness (reverse implication failure) Intermediate notions
verbal subgroup generated by a set of words |FULL LIST, MORE INFO
existentially bound-word subgroup similar definition, but we use only existential quantifiers |FULL LIST, MORE INFO
marginal subgroup |FULL LIST, MORE INFO
weakly marginal subgroup |FULL LIST, MORE INFO

Weaker properties

Property Meaning Proof of implication Proof of strictness (reverse implication failure) Intermediate notions
strictly characteristic subgroup Bound-word implies strictly characteristic |FULL LIST, MORE INFO
characteristic subgroup (via strictly characteristic) (via strictly characteristic) |FULL LIST, MORE INFO
normal subgroup (via characteristic) (via characteristic) Characteristic subgroup|FULL LIST, MORE INFO