We construct an explicit infinite family of pairwise non-isomorphic infinite simple groups of type F infinity (in particular, they are finitely presented) that act faithfully on the circle by orientation-preserving homeomorphisms, but that admit neither non-trivial piecewise affine nor piecewise projective actions on the projective line. Our examples are certain forest-skein groups which, informally, are a mixture of Richard Thompson's groups with Vaughan Jones' planar algebras.
Finitely presented simple groups with no piecewise projective actions / Brothier, A.; Seelig, R.. - In: JOURNAL OF THE LONDON MATHEMATICAL SOCIETY. - ISSN 1469-7750. - 113:1(2026), pp. e70436.1-e70436.36. [10.1112/jlms.70436]
Finitely presented simple groups with no piecewise projective actions
Brothier A.;
2026-01-01
Abstract
We construct an explicit infinite family of pairwise non-isomorphic infinite simple groups of type F infinity (in particular, they are finitely presented) that act faithfully on the circle by orientation-preserving homeomorphisms, but that admit neither non-trivial piecewise affine nor piecewise projective actions on the projective line. Our examples are certain forest-skein groups which, informally, are a mixture of Richard Thompson's groups with Vaughan Jones' planar algebras.Pubblicazioni consigliate
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