Effective categoricity of equivalence structures

Annals of Pure and Applied Logic 141 (1):61-78 (2006)

Valentina Harizanov
George Washington University
We investigate effective categoricity of computable equivalence structures . We show that is computably categorical if and only if has only finitely many finite equivalence classes, or has only finitely many infinite classes, bounded character, and at most one finite k such that there are infinitely many classes of size k. We also prove that all computably categorical structures are relatively computably categorical, that is, have computably enumerable Scott families of existential formulas. Since all computable equivalence structures are relatively categorical, we further investigate when they are categorical. We also obtain results on the index sets of computable equivalence structures
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DOI 10.1016/j.apal.2005.10.002
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References found in this work BETA

Effective Content of Field Theory.G. Metakides - 1979 - Annals of Pure and Applied Logic 17 (3):289.
Generic Copies of Countable Structures.Chris Ash, Julia Knight, Mark Manasse & Theodore Slaman - 1989 - Annals of Pure and Applied Logic 42 (3):195-205.
Computable Models of Theories with Few Models.Bakhadyr Khoussainov, Andre Nies & Richard A. Shore - 1997 - Notre Dame Journal of Formal Logic 38 (2):165-178.

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On Δ 2 0 -Categoricity of Equivalence Relations.Rod Downey, Alexander G. Melnikov & Keng Meng Ng - 2015 - Annals of Pure and Applied Logic 166 (9):851-880.

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