Simple groups separated by finiteness properties
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Abstract
We show that for every positive integer n there exists a simple group that is of type \(\mathrm {F}_{n-1}\) but not of type \(\mathrm {F}_n\). For \(n\ge 3\) these groups are the first known examples of this kind. They also provide infinitely many quasi-isometry classes of finitely presented simple groups. The only previously known infinite family of such classes, due to Caprace–Rémy, consists of non-affine Kac–Moody groups over finite fields. Our examples arise from Röver–Nekrashevych groups, and contain free abelian groups of infinite rank.
Mathematics Subject Classification
Primary 20E32 Secondary 57M07 20F65 20E08Notes
Acknowledgements
We are grateful to Dessislava Kochloukova and Said Sidki for sharing a preprint of [36] with us and to Bertrand Rémy for asking the question that motivated our search for simple groups separated by finiteness properties. We also thank Matt Brin, Pierre-Emmanuel Caprace, Eduard Schesler, and Marco Varisco for many helpful comments.
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