A compact space with a measure that knows which sets are homeomorphic (Q791089)
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scientific article; zbMATH DE number 3849823
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | A compact space with a measure that knows which sets are homeomorphic |
scientific article; zbMATH DE number 3849823 |
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A compact space with a measure that knows which sets are homeomorphic (English)
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1984
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In this paper it is constructed a compact space bH which has a Borel measure \(\bar{\bar\mu}\) which knows which sets are homeomorphic: if X and Y are homeomorphic Borel sets then \(\bar{\bar \mu}(X)=\bar{\bar\mu}(Y)\), and as a partial converse, if X and Y are open and \(\bar{\bar \mu}(X)=\bar{\bar\mu}(Y)\) and X and Y are both compact or both noncompact, then X and Y are homeomorphic. In particular, \(\bar{\bar\mu}\) is nonzero and invariant under all autohomeomorphisms; it turns out that up to a multiplicative constant \(\bar{\bar\mu}\) is unique with respect to these properties. bH is constructed as an easy to visualize compactification of a very special subgroup H of the circle group T; the Haar measure \(\mu\) on T induces \(\bar{\bar\mu}\) and also induces a measure \({\bar\mu}\) on H which knows which subsets of H are homeomorphic.
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compact homogeneous space
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Borel measure
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homeomorphic
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compactification
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subgroup of circle group
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homeomorphic invariant measure
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