Quotients by countable normal subgroups are hyperfinite (Q6062652)
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scientific article; zbMATH DE number 7761459
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | Quotients by countable normal subgroups are hyperfinite |
scientific article; zbMATH DE number 7761459 |
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Quotients by countable normal subgroups are hyperfinite (English)
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6 November 2023
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Summary: We show that for any Polish group \(G\) and any countable normal subgroup \(\Gamma \triangleleft G\), the coset equivalence relation \(G/\Gamma\) is a hyperfinite Borel equivalence relation. In particular, the outer automorphism group of any countable group is hyperfinite.
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descriptive set theory
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Borel equivalence relation
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Polish group
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hyperfinite
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