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The Branching Theorem and Computable Categoricity in the Ershov Hierarchy

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Algebra and Logic Aims and scope

Computable categoricity in the Ershov hierarchy is studied. We consider F a -categorical and G a -categorical structures. These were introduced by B. Khoussainov, F. Stephan, and Y. Yang for a, which is a notation for a constructive ordinal. A generalization of the branching theorem is proved for F a -categorical structures. As a consequence we obtain a description of F a -categorical structures for classes of Boolean algebras and Abelian p-groups. Furthermore, it is shown that the branching theorem cannot be generalized to Ga-categorical structures.

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Correspondence to N. A. Bazhenov.

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Supported by RFBR (project No. 14-01-00376), by the Grants Council (under RF President) for State Aid of Leading Scientific Schools (grant NSh-860.2014.1), and by the Russian Ministry of Education and Science (gov. contract No. 2014/139).

Translated from Algebra i Logika, Vol. 54, No. 2, pp. 137–157,March-April, 2015.

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Bazhenov, N.A. The Branching Theorem and Computable Categoricity in the Ershov Hierarchy. Algebra Logic 54, 91–104 (2015). https://doi.org/10.1007/s10469-015-9329-6

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  • DOI: https://doi.org/10.1007/s10469-015-9329-6

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