Abstract:
We say that a structure is categorical relative to n-decidable presentations (or autostable relative to n-constructivizations) if any two n-decidable copies of the structure are computably isomorphic. For n=0, we have the classical definition of a computably categorical (autostable) structure. Downey, Kach, Lempp, Lewis, Montalbán, and Turetsky proved that there is no simple syntactic characterization of computable categoricity. More formally, they showed that the index set of computably categorical structures is Π11-complete.
We study index sets of n-decidable structures that are categorical relative to m-decidable presentations, for various m,n∈ω. If m⩾n⩾0, then the index set is again Π11-complete, i.e., there is no nice description of the class of n-decidable structures that are categorical relative to m-decidable presentations. In the case m=n−1⩾0, the index set is Π04-complete, while if 0⩽m⩽n−2, the index set is Σ03-complete.
Keywords:
index set, structure categorical relative to n-decidable presentations, n-decidable structure categorical relative to m-decidable presentations.
Supported by Austrian Science Fund FWF (projects V 206 and I 1238).
Supported by RFBR (project No. 13-01-91001-ANF_a) and by the Grants Council (under RF President) for State Aid of Leading Scientific Schools (grant NSh-860.2014.1).
Citation:
E. B. Fokina, S. S. Goncharov, V. Harizanov, O. V. Kudinov, D. Turetsky, “Index sets for n-decidable structures categorical relative to m-decidable presentations”, Algebra Logika, 54:4 (2015), 520–528; Algebra and Logic, 54:4 (2015), 336–341
This publication is cited in the following 11 articles:
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M. N. Gaskova, “Boolean Algebras Autostable Relative to n-Decidable Presentations”, Algebra Logic, 61:4 (2022), 301
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