Upper bounds on ideals in the computably enumerable Turing degrees (Q639654)
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scientific article; zbMATH DE number 5949177
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | Upper bounds on ideals in the computably enumerable Turing degrees |
scientific article; zbMATH DE number 5949177 |
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Upper bounds on ideals in the computably enumerable Turing degrees (English)
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22 September 2011
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In this paper the following interesting results are obtained. Every proper \(\Sigma^0_4\) ideal of the c.e. Turing degrees has an incomplete upper bound. Every proper \(\Sigma^0_3\) ideal in the c.e. Turing degrees has a low\(_2\) upper bound. The partial order of \(\Sigma^0_3\) ideals under inclusion in the c.e. degrees is dense.
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Turing degrees
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ideals
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arithmetical hierarchy
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