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Published online by Cambridge University Press: 23 December 2024
The group of order-preserving automorphisms of a finitely generated Archimedean ordered group of rank  $2$ is either infinite cyclic or trivial according as the ratio in
$2$ is either infinite cyclic or trivial according as the ratio in  $\mathbb {R}$ of the generators of the subgroup is or is not quadratic over
$\mathbb {R}$ of the generators of the subgroup is or is not quadratic over  $\mathbb {Q}.$ In the case of an Archimedean ordered group of rank
$\mathbb {Q}.$ In the case of an Archimedean ordered group of rank  $2$ that is not finitely generated, the group of order-preserving automorphisms is free abelian. Criteria determining the rank of this free abelian group are established.
$2$ that is not finitely generated, the group of order-preserving automorphisms is free abelian. Criteria determining the rank of this free abelian group are established.
 $\sqrt{D}$
and
$\sqrt{D}$
and 
 $\frac{1}{2}\left(1+\sqrt{D}\;\right)$
. Proc. Amer. Math. Soc. 120(1994), no. 4, 995–1002.Google Scholar
$\frac{1}{2}\left(1+\sqrt{D}\;\right)$
. Proc. Amer. Math. Soc. 120(1994), no. 4, 995–1002.Google Scholar