Alexander polynomial obstruction of bi-orderability for rationally   homologically fibered knot groups
  We show that if the fundamental group of the complement of a rationally homologically fibered knot in a rational homology 3-sphere is bi-orderable, then its Alexander polynomial has at least one positive real root. Our argument can be applied for a finitely generated group which is an HNN extension with certain properties. 
Tetsuya Ito
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