Abstract
P. Hall constructed a universal countable locally finite group U, determined up to isomorphism by two properties: every finite group C is a subgroup of U, and every embedding of C into U is conjugate in U. Every countable locally finite group is a subgroup of U. We prove that U is a subgroup of the abstract commensurator of a finite-rank nonabelian free group.
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EB was supported by the Azrieli Foundation.
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Bering, E.A., Studenmund, D. Hall’s universal group is a subgroup of the abstract commensurator of a free group. Isr. J. Math. (2023). https://doi.org/10.1007/s11856-023-2591-8
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DOI: https://doi.org/10.1007/s11856-023-2591-8