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Finitely presented left orderable monsters
- Part of
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- Journal:
- Ergodic Theory and Dynamical Systems / Volume 44 / Issue 5 / May 2024
- Published online by Cambridge University Press:
- 06 July 2023, pp. 1367-1378
- Print publication:
- May 2024
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- Article
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A left orderable monster is a finitely generated left orderable group all of whose fixed point-free actions on the line are proximal: the action is semiconjugate to a minimal action so that for every bounded interval I and open interval J, there is a group element that sends I into J. In his 2018 ICM address, Navas asked about the existence of left orderable monsters. By now there are several examples, all of which are finitely generated but not finitely presentable. We provide the first examples of left orderable monsters that are finitely presentable, and even of type
$F_\infty $. These groups satisfy several additional properties separating them from the previous examples: they are not simple, they act minimally on the circle, and they have an infinite-dimensional space of homogeneous quasimorphisms. Our construction is flexible enough that it produces infinitely many isomorphism classes of finitely presented (and type 
$F_{\infty }$) left orderable monsters.
