The Kierstead's conjecture and limitwise monotonic functions (Q1709678)
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scientific article; zbMATH DE number 6856630
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | The Kierstead's conjecture and limitwise monotonic functions |
scientific article; zbMATH DE number 6856630 |
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The Kierstead's conjecture and limitwise monotonic functions (English)
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6 April 2018
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A linear order is \(\Pi_1^0\)-rigid if it does not have any nontrivial \(\Pi_1^0\)-automorphism. Let \(\zeta, \eta\) are the order types integers and rational numbers, respectively. \textit{H. A. Kierstead} [J. Symb. Log. 52, 681--688 (1987; Zbl 0637.03043)] conjectured that every computable copy of a linear order \(\mathcal L\) has a strongly nontrivial \(\Pi_1^0\)-automorphism if and only if \(\mathcal L\) contains an interval of order type \(\eta\). In the paper under review, the authors prove this conjecture for linear orders whose order types are \(\Sigma_{q\in Q}F(q)\), where \(F\) is an extended \(\emptyset'\)-limitwise monotonic function, i.e. \(F\) can take the value \(\zeta\).
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recursive linear order
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automorphism
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limitwise monotonic function
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