The Complexity of Tukey Types and Cofinal Types

  • Marie NicholsonEmail author
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 10936)


This paper studies how difficult it is to determine whether two computable partial orders share the same Tukey type and the same cofinal type. For Tukey types, we show the index set is \(\mathbf {0}^{(3)}\). For cofinal types, the we shows the index set is computable from \(\mathbf {0}^{(4)}\). This is in sharp contrast to the isomorphism problem for computable partial orders, which is \(\varSigma ^1_1\).


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© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Cork Institute of TechnologyCorkIreland

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