A conjecture of Ershov for a relative hierarchy fails near \({\mathcal O}\) (Q796522)
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scientific article; zbMATH DE number 3865260
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | A conjecture of Ershov for a relative hierarchy fails near \({\mathcal O}\) |
scientific article; zbMATH DE number 3865260 |
Statements
A conjecture of Ershov for a relative hierarchy fails near \({\mathcal O}\) (English)
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1983
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Significant properties, of the transfinite difference hierarchy based on recursively enumerable sets, were developed in work of Yu. L. Ershov. Relativization of the hierarchy is a natural topic and, in addition to the obvious means of relativization, Ershov conjectured that two weak relativizations may be equivalent to full relativization. The paper being reviewed refutes one of these conjectures.
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Kleene's 0
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transfinite difference hierarchy
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Relativization
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