9 found
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  1.  20
    Bounding Nonsplitting Enumeration Degrees.Thomas F. Kent & Andrea Sorbi - 2007 - Journal of Symbolic Logic 72 (4):1405 - 1417.
    We show that every nonzero $\Sigma _{2}^{0}$ enumeration degree bounds a nonsplitting nonzero enumeration degree.
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  2.  49
    A note on the enumeration degrees of 1-generic sets.Liliana Badillo, Caterina Bianchini, Hristo Ganchev, Thomas F. Kent & Andrea Sorbi - 2016 - Archive for Mathematical Logic 55 (3-4):405-414.
    We show that every nonzero Δ20\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\Delta^{0}_{2}}$$\end{document} enumeration degree bounds the enumeration degree of a 1-generic set. We also point out that the enumeration degrees of 1-generic sets, below the first jump, are not downwards closed, thus answering a question of Cooper.
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  3.  15
    The Π₃-Theory of the [image] -Enumeration Degrees Is Undecidable.Thomas F. Kent - 2006 - Journal of Symbolic Logic 71 (4):1284 - 1302.
    We show that in the language of {≤}, the Π₃-fragment of the first order theory of the $\Sigma _{2}^{0}$-enumeration degrees is undecidable. We then extend this result to show that the Π₃-theory of any substructure of the enumeration degrees which contains the $\Delta _{2}^{0}$-degrees is undecidable.
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  4.  46
    Empty intervals in the enumeration degrees.Thomas F. Kent, Andrew Em Lewis & Andrea Sorbi - 2012 - Annals of Pure and Applied Logic 163 (5):567-574.
  5.  15
    Interpreting true arithmetic in the Δ 0 2 -enumeration degrees.Thomas F. Kent - 2010 - Journal of Symbolic Logic 75 (2):522-550.
    We show that there is a first order sentence φ(x; a, b, l) such that for every computable partial order.
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  6.  18
    The structure of the s -degrees contained within a single e -degree.Thomas F. Kent - 2009 - Annals of Pure and Applied Logic 160 (1):13-21.
    For any enumeration degree let be the set of s-degrees contained in . We answer an open question of Watson by showing that if is a nontrivial -enumeration degree, then has no least element. We also show that every countable partial order embeds into . Finally, we construct -sets A and B such that B≤eA but for every X≡eB, XsA.
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  7.  9
    The Π₃-Theory of the $\Sigma _{2}^{0}$ -Enumeration Degrees Is Undecidable.Thomas F. Kent - 2006 - Journal of Symbolic Logic 71 (4):1284 - 1302.
    We show that in the language of {≤}, the Π₃-fragment of the first order theory of the $\Sigma _{2}^{0}$-enumeration degrees is undecidable. We then extend this result to show that the Π₃-theory of any substructure of the enumeration degrees which contains the $\Delta _{2}^{0}$-degrees is undecidable.
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  8.  81
    Branching in the $${\Sigma^0_2}$$ -enumeration degrees: a new perspective. [REVIEW]Maria L. Affatato, Thomas F. Kent & Andrea Sorbi - 2008 - Archive for Mathematical Logic 47 (3):221-231.
    We give an alternative and more informative proof that every incomplete ${\Sigma^{0}_{2}}$ -enumeration degree is the meet of two incomparable ${\Sigma^{0}_{2}}$ -degrees, which allows us to show the stronger result that for every incomplete ${\Sigma^{0}_{2}}$ -enumeration degree a, there exist enumeration degrees x 1 and x 2 such that a, x 1, x 2 are incomparable, and for all b ≤ a, b = (b ∨ x 1 ) ∧ (b ∨ x 2 ).
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  9.  5
    Branching in the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\Sigma^0_2}$$\end{document} -enumeration degrees: a new perspective. [REVIEW]Maria L. Affatato, Thomas F. Kent & Andrea Sorbi - 2008 - Archive for Mathematical Logic 47 (3):221-231.
    We give an alternative and more informative proof that every incomplete \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\Sigma^{0}_{2}}$$\end{document} -enumeration degree is the meet of two incomparable \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\Sigma^{0}_{2}}$$\end{document} -degrees, which allows us to show the stronger result that for every incomplete \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\Sigma^{0}_{2}}$$\end{document} -enumeration degree a, there exist enumeration degrees x1 and x2 such that a, x1, x2 are incomparable, and for (...)
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