The space of relative orders and a generalization of Morris indicability theorem

Abstract

We introduce the space of relative orders on a group and show that it is compact whenever the group is finitely generated. We use this to show that if $G$ is a finitely generated group acting by order preserving homeomorphism of on the line, then if some stabilizer of a point is proper and co-amenable subgroup, then $G$ surjects onto $\mathbb{Z}$. This is a generalization of a theorem of Morris.

v2: 10 pages, 2 figures. Typos corrected, Lemma 3.3 split into two statements affecting the numbering