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Bi-orders do not arise from total orders (2004.13798v1)
Published 28 Apr 2020 in math.GR and math.LO
Abstract: We present some Zermelo-Fraenkel consistency results regarding bi-orderability of groups, as well as a construction of groups with Conradian orders whose every action on metric spaces has bounded orbits. A classical consequence of the ultrafilter lemma is that a group is bi-orderable if and only if it is locally bi-orderable. We show that there exists a model of ZF in which there is a group which is locally free (ergo locally bi-orderable) and not bi-orderable, and the group can be given a total order. Such a group can also exist in the presence of the principle of dependent choices. Comparable consistency results are provided for torsion-free abelian groups.