On the automorphism group of the countable dense circular order
Volume 204 / 2009
Fundamenta Mathematicae 204 (2009), 97-111
MSC: Primary 06F99.
DOI: 10.4064/fm204-2-1
Abstract
Let $(C,R)$ be the countable dense circular ordering, and $G$ its automorphism group. It is shown that certain properties of group elements are first order definable in $G$, and these results are used to reconstruct $C$ inside $G$, and to demonstrate that its outer automorphism group has order 2. Similar statements hold for the completion $\overline C$.
