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[parent] isolated subgroup (Definition)

Let $G$ be a multiplicative ordered group and $F$ its subgroup. We call this subgroup isolated if every element $f$ of $F$ and every element $g$ of $G$ satisfy $$f \leqq g \leqq 1 \,\,\,\Rightarrow \,\, g\in F.$$

If an ordered group $G$ has only a finite number of isolated subgroups, then the number of proper ($\neq G$ ) isolated subgroups of $G$ is the rank of $G$ .

Theorem 1   Let $G$ be an abelian ordered group with order at least 2. The rank of $G$ equals one iff there is an order-preserving isomorphism from $G$ onto some subgroup of the multiplicative group of real numbers.

Bibliography

1
M. LARSEN & P. MCCARTHY: Multiplicative theory of ideals. Academic Press. New York (1971).




"isolated subgroup" is owned by pahio.
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See Also: rank of valuation, Krull valuation

Also defines:  rank of ordered group

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Attachments:
characterization of ordered groups of rank one (Theorem) by rspuzio
proof of embedding theorem for ordered abelian groups of rank one (Proof) by rspuzio
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Cross-references: real numbers, multiplicative group, onto, isomorphism, order-preserving, iff, abelian, number, finite, element, subgroup, ordered group
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This is version 10 of isolated subgroup, born on 2004-12-29, modified 2009-02-22.
Object id is 6605, canonical name is IsolatedSubgroup.
Accessed 2487 times total.

Classification:
AMS MSC06A05 (Order, lattices, ordered algebraic structures :: Ordered sets :: Total order)
 20F60 (Group theory and generalizations :: Special aspects of infinite or finite groups :: Ordered groups)

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