Weakly Precomplete Equivalence Relations in the Ershov Hierarchy
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DOI: 10.1007/s10469-019-09538-y
Abstract: We study the computable reducibility ≤c for equivalence relations in the Ershov hierarchy. For an arbitrary notation a for a nonzero computable ordinal, it is stated that there exist a $$ {\varPi}_a^{-1} $$ -universal equivalence… read more here.
Keywords: weakly precomplete; equivalence; equivalence relations; relations ershov ... See more keywords
Rogers Semilattices for Families of Equivalence Relations in the Ershov Hierarchy
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DOI: 10.1134/s0037446619020046
Abstract: The paper studies Rogers semilattices for families of equivalence relations in the Ershov hierarchy. For an arbitrary notation a of a nonzero computable ordinal, we consider $$\sum\nolimits_a^{- 1} {}$$∑a−1-computable numberings of the family of all… read more here.
Keywords: equivalence relations; rogers semilattices; ershov hierarchy; semilattices families ... See more keywords
Computable Linear Orders and the Ershov Hierarchy
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DOI: 10.3103/s1066369x18010085
Abstract: We give the collection of relations on computable linear orders. For any natural number n, the degree spectrum of such relations of some computable linear orders contains exactly all n-computable enumerable degrees. We also study… read more here.
Keywords: computable linear; orders ershov; linear orders; ershov hierarchy ... See more keywords