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  1. The Isomorphism Problem for Computable Abelian p-Groups of Bounded Length.Wesley Calvert - 2005 - Journal of Symbolic Logic 70 (1):331 - 345.
    Theories of classification distinguish classes with some good structure theorem from those for which none is possible. Some classes (dense linear orders, for instance) are non-classifiable in general, but are classifiable when we consider only countable members. This paper explores such a notion for classes of computable structures by working out a sequence of examples. We follow recent work by Goncharov and Knight in using the degree of the isomorphism problem for a class to distinguish classifiable classes from non-classifiable. In (...)
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  • Requirement systems.Julia F. Knight - 1995 - Journal of Symbolic Logic 60 (1):222-245.
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  • Incomparable prime ideals of recursively enumerable degrees.William C. Calhoun - 1993 - Annals of Pure and Applied Logic 63 (1):39-56.
    Calhoun, W.C., Incomparable prime ideals of recursively enumerable degrees, Annals of Pure and Applied Logic 63 39–56. We show that there is a countably infinite antichain of prime ideals of recursively enumerable degrees. This solves a generalized form of Post's problem.
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  • Mixed systems.C. J. Ash & J. F. Knight - 1994 - Journal of Symbolic Logic 59 (4):1383-1399.
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  • A construction for recursive linear orderings.C. J. Ash - 1991 - Journal of Symbolic Logic 56 (2):673-683.
    We re-express a previous general result in a way which seems easier to remember, using the terminology of infinite games. We show how this can be applied to construct recursive linear orderings, showing, for example, that if there is a ▵ 0 2β + 1 linear ordering of type τ, then there is a recursive ordering of type ω β · τ.
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  • Degrees of categoricity on a Cone via η-systems.Barbara F. Csima & Matthew Harrison-Trainor - 2017 - Journal of Symbolic Logic 82 (1):325-346.
    We investigate the complexity of isomorphisms of computable structures on cones in the Turing degrees. We show that, on a cone, every structure has a strong degree of categoricity, and that degree of categoricity is${\rm{\Delta }}_\alpha ^0 $-complete for someα. To prove this, we extend Montalbán’sη-system framework to deal with limit ordinals in a more general way. We also show that, for any fixed computable structure, there is an ordinalαand a cone in the Turing degrees such that the exact complexity (...)
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  • Priority arguments via true stages.Antonio Montalbán - 2014 - Journal of Symbolic Logic 79 (4):1315-1335.
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  • Ramified systems.C. J. Ash & J. F. Knight - 1994 - Annals of Pure and Applied Logic 70 (3):205-221.
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  • Inseparability in recursive copies.Kevin J. Davey - 1994 - Annals of Pure and Applied Logic 68 (1):1-52.
    In [7] and [8], it is established that given any abstract countable structure S and a relation R on S, then as long as S has a recursive copy satisfying extra decidability conditions, R will be ∑0α on every recursive copy of S iff R is definable in S by a special type of infinitary formula, a ∑rα() formula. We generalize the typ e of constructions of these papers to produce conditions under which, given two disjoint relations R1 and R2 (...)
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  • A general framework for priority arguments.Steffen Lempp & Manuel Lerman - 1995 - Bulletin of Symbolic Logic 1 (2):189-201.
    The degrees of unsolvability were introduced in the ground-breaking papers of Post [20] and Kleene and Post [7] as an attempt to measure theinformation contentof sets of natural numbers. Kleene and Post were interested in the relative complexity of decision problems arising naturally in mathematics; in particular, they wished to know when a solution to one decision problem contained the information necessary to solve a second decision problem. As decision problems can be coded by sets of natural numbers, this question (...)
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  • Annual meeting of the association for symbolic logic: Notre dame, 1993.Steven Buechler - 1994 - Journal of Symbolic Logic 59 (2):696-719.
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  • The property “arithmetic-is-recursive” on a cone.Uri Andrews, Matthew Harrison-Trainor & Noah Schweber - 2021 - Journal of Mathematical Logic 21 (3):2150021.
    We say that a theory [Formula: see text] satisfies arithmetic-is-recursive if any [Formula: see text]-computable model of [Formula: see text] has an [Formula: see text]-computable copy; that is, the models of [Formula: see text] satisfy a sort of jump inversion. We give an example of a theory satisfying arithmetic-is-recursive non-trivially and prove that the theories satisfying arithmetic-is-recursive on a cone are exactly those theories with countably many [Formula: see text]-back-and-forth types.
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  • Coding a family of sets.J. F. Knight - 1998 - Annals of Pure and Applied Logic 94 (1-3):127-142.
    In this paper, we state a metatheorem for constructions involving coding. Using the metatheorem, we obtain results on coding a family of sets into a family of relations, or into a single relation. For a concrete example, we show that the set of limit points in a recursive ordering of type ω 2 can have arbitrary 2-REA degree.
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  • Hyperarithmetical relations in expansions of recursive structures.Alan D. Vlach - 1994 - Annals of Pure and Applied Logic 66 (2):163-196.
    Let be a model of a theory T. Depending on wether is decidable or recursive, and on whether T is strongly minimal or -minimal, we find conditions on which guarantee that every infinite independent subset of is not recursively enumerable. For each of the same four cases we also find conditions on which guarantee that every infinite independent subset of has Turing degree 0'. More generally, let be a recursive -structure, R a relation symbol not in , ψ a recursive (...)
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