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.
Similar content being viewed by others
References
Yu. L. Ershov, “On a hierarchy of sets I,” Algebra and Logic, 7, No. 1, 25–43 (1968).
Yu. L. Ershov, “On a hierarchy of sets II,” Algebra and Logic, 7, No. 4, 212–232 (1968).
Yu. L. Ershov, “On a hierarchy of sets III,” Algebra and Logic, 9, No. 1, 20–31 (1970).
S. S. Goncharov, S. Lempp, and D. R. Solomon, “Friedberg numberings of families of ncomputably enumerable sets,” Algebra and Logic, 41, No. 2, 81–86 (2002).
S. A. Badaev and S. Lempp, “A decomposition of the Rogers semilattice of a family of d.c.e. sets,” J. Symb. Log., 74, No. 2, 618–640 (2009).
S. S. Ospichev, “Properties of numberings in various levels of the Ershov hierarchy,” Vestnik NGU, Mat., Mekh., Inf., 10, No. 4, 125–132 (2010).
S. Ospichev, “Computable family of Σ a −1 -sets without Friedberg numberings,” in 6th Conf. Comput. Europe, CiE 2010, Ponta Delgada, Azores (2010), pp. 311–315.
S. S. Ospichev, “Infinite family of Σ a −1 -sets with a unique computable numbering,” Vestnik NGU, Mat., Mekh., Inf., 11, No. 2, 89–92 (2011).
M. Manat and A. Sorbi, “Positive undecidable numberings in the Ershov hierarchy,” Algebra and Logic, 50, No. 6, 512–525 (2011).
S. A. Badaev, M. Manat, and A. Sorbi, “Rogers semilattices of families of two embedded sets in the Ershov hierarchy,” Math. Log. Q., 58, Nos. 4/5, 366–376 (2012).
B. Khoussainov, F. Stephan, and Y. Yang, “Computable categoricity and the Ershov hierarchy,” Ann. Pure Appl. Log., 156, No. 1, 86–95 (2008).
D. Cenzer, G. LaForte, and J. B. Remmel, “Equivalence structures and isomorphisms in the difference hierarchy,” J. Symb. Log., 74, No. 2, 535–556 (2009).
S. S. Goncharov and V. D. Dzgoev, “Autostability of models,” Algebra and Logic, 19, No. 1, 28–36 (1980).
S. S. Goncharov, “Autostability of models and Abelian groups,” Algebra and Logic, 19, No. 1, 13–27 (1980).
P. E. Alaev, “Autostable I-algebras,” Algebra and Logic, 43, No. 5, 285–306 (2004).
D. I. Dushenin, “Relative autostability of direct sums of Abelian p-groups,” Vestnik NGU, Mat., Mekh., Inf., 10, No. 1, 29–39 (2010).
N. T. Kogabaev, “Autostability of Boolean algebras with distinguished ideal,” Sib. Math. J., 39, No. 5, 927–935 (1998).
P. E. Alaev, “Computably categorical Boolean algebras enriched by ideals and atoms,” Ann. Pure Appl. Log., 163, No. 5, 485–499 (2012).
N. T. Kogabaev, “The class of projective planes is noncomputable,” Algebra and Logic, 47, No. 4, 242–257 (2008).
N. T. Kogabaev, “Noncomputability of classes of pappian and desarguesian projective planes,” Sib. Math. J., 54, No. 2, 247–255 (2013).
R. R. Tukhbatullina, “Autostability of the Boolean algebra B ω expanded by an automorphism,” Vestnik NGU, Mat., Mekh., Inf., 10, No. 3, 110–118 (2010).
S. S. Goncharov and Yu. L. Ershov, Constructive Models, Sib. School Alg. Log. [in Russian], Nauch. Kniga, Novosibirsk (1999).
C. J. Ash and J. F. Knight, Computable Structures and the Hyperarithmetical Hierarchy, Stud. Logic Found. Math., 144, Elsevier, Amsterdam (2000).
H. Rogers, Theory of Recursive Functions and Effective Computability, McGraw-Hill, New York (1967).
J. B. Remmel, “Recursively categorical linear orderings,” Proc. Am. Math. Soc., 83, No. 2, 387–391 (1981).
J. B. Remmel, “Recursive isomorphism types of recursive Boolean algebras,” J. Symb. Log., 46, No. 3, 572–594 (1981).
L. Fuchs, Infinite Abelian Groups, Vol. 1, Academic Press, New York (1970).
R. L. Smith, “Two theorems on autostability in p-groups,” in Lect. Notes Math., 859 (1981), pp. 302–311.
Author information
Authors and Affiliations
Corresponding author
Additional information
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.
Rights and permissions
About this article
Cite this article
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
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10469-015-9329-6