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  1. Investigating the Computable Friedman–Stanley Jump.Uri Andrews & Luca San Mauro - forthcoming - Journal of Symbolic Logic:1-27.
    The Friedman–Stanley jump, extensively studied by descriptive set theorists, is a fundamental tool for gauging the complexity of Borel isomorphism relations. This paper focuses on a natural computable analog of this jump operator for equivalence relations on $\omega $, written ${\dotplus }$, recently introduced by Clemens, Coskey, and Krakoff. We offer a thorough analysis of the computable Friedman–Stanley jump and its connections with the hierarchy of countable equivalence relations under the computable reducibility $\leq _c$. In particular, we show that this (...)
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  • On the Degree Structure of Equivalence Relations Under Computable Reducibility.Keng Meng Ng & Hongyuan Yu - 2019 - Notre Dame Journal of Formal Logic 60 (4):733-761.
    We study the degree structure of the ω-c.e., n-c.e., and Π10 equivalence relations under the computable many-one reducibility. In particular, we investigate for each of these classes of degrees the most basic questions about the structure of the partial order. We prove the existence of the greatest element for the ω-c.e. and n-computably enumerable equivalence relations. We provide computable enumerations of the degrees of ω-c.e., n-c.e., and Π10 equivalence relations. We prove that for all the degree classes considered, upward density (...)
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  • On the Structure of Computable Reducibility on Equivalence Relations of Natural Numbers.Uri Andrews, Daniel F. Belin & Luca San Mauro - 2023 - Journal of Symbolic Logic 88 (3):1038-1063.
    We examine the degree structure $\operatorname {\mathrm {\mathbf {ER}}}$ of equivalence relations on $\omega $ under computable reducibility. We examine when pairs of degrees have a least upper bound. In particular, we show that sufficiently incomparable pairs of degrees do not have a least upper bound but that some incomparable degrees do, and we characterize the degrees which have a least upper bound with every finite equivalence relation. We show that the natural classes of finite, light, and dark degrees are (...)
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