We use the Low Basis Theorem of Jockusch and Soare
to show that all computable algebraic fields
are d-computably categorical for a
particular Turing degree d with d'=0'',
but that not all such fields are 0'-computably
categorical. We also prove related results about
algebraic fields with splitting algorithms,
and fields of finite transcendence degree over ℚ.
References
C.J. Ash, J.F. Knight, M.S. Manasse, and T.A. Slaman, Generic copies of countable structures, Annals of Pure and Applied Logic, vol. 42 (1989), pp. 195--205.
Mathematical Reviews (MathSciNet):
MR998606
W. Calvert, V. Harizanov, and A. Shlapentokh, Turing degrees of the isomorphism types of algebraic objects, Journal of London Mathematical Society, vol. 73 (2007), pp. 273--286.
D. Cenzer, $\Pi^0_1$-classes in recursion theory, Handbook of computability theory (E.R. Griffor, editor), Elsevier, Amsterdam, 1999, pp. 37--85.
R.G. Downey and Jr. C.G. Jockusch, Every low Boolean algebra is isomorphic to a recursive one, Proceedings of the American Mathematical Society, vol. 122, 1994, pp. 871--880.
R.G. Downey, D.R. Hirschfeldt, and B. Khoussainov, Uniformity in computable structure theory, Algebra and Logic, vol. 42 (2003), pp. 318--332.
H.M. Edwards, Galois theory, Springer-Verlag, New York, 1984.
Mathematical Reviews (MathSciNet):
MR743418
Y.L. Ershov and S.S. Goncharov, Constructive fields, Constructive models, Kluwer Academic/Plenum Press, New York, 2000, Section 2.5.
Yu.L. Ershov, Theorie der Numerierungen, Zeitschrift für Mathematische Logik und Grundlagen der Mathematik, vol. 23 (1977), pp. 289--371.
Mathematical Reviews (MathSciNet):
MR439603
E. Fokina, I. Kalimullin, and R.G. Miller, Degrees of categoricity of computable structures, to appear.
M.D. Fried and M. Jarden, Field arithmetic, Springer-Verlag, Berlin, 1986.
Mathematical Reviews (MathSciNet):
MR868860
A. Frohlich and J.C. Shepherdson, Effective procedures in field theory, The Philosophical Transactions of the Royal Society, Series A, vol. 248 (1956), no. 950, pp. 407--432.
Mathematical Reviews (MathSciNet):
MR74349
S.S. Goncharov, Autostability and computable families of constructivizations, Algebra and Logic, vol. 14 (1975), pp. 647--680, (Russian), 392--409 (English translation).
Mathematical Reviews (MathSciNet):
MR437335
--------, Nonequivalent constructivizations, Proc. Math. Inst. Sib. Branch Acad. Sci., Nauka, Novosibirsk, 1982.
--------, Autostable models and algorithmic dimensions, Handbook of recursive mathematics, vol. 1, Elsevier, Amsterdam, 1998, pp. 261--287.
S.S. Goncharov and V.D. Dzgoev, Autostability of models, Algebra and Logic, vol. 19 (1980), pp. 45--58, (Russian), 28-37 (English translation).
Mathematical Reviews (MathSciNet):
MR604657
S.S. Goncharov, S. Lempp, and R. Solomon, The computable dimension of ordered abelian groups, Advances in Mathematics, vol. 175 (2003), no. 1, pp. 102--143.
D.R. Hirschfeldt, B. Khoussainov, R.A. Shore, and A.M. Slinko, Degree spectra and computable dimensions in algebraic structures, Annals of Pure and Applied Logic, vol. 115 (2002), pp. 71--113.
N. Jacobson, Basic algebra I, W.H. Freeman & Co., New York, 1985.
Mathematical Reviews (MathSciNet):
MR780184
C.G. Jockusch and R.I. Soare, $\Pi^0_1$-classes and degrees of theories, Transactions of the American Mathematical Society, vol. 173 (1972), pp. 33--56.
Mathematical Reviews (MathSciNet):
MR316227
--------, Degrees of orderings not isomorphic to recursive linear orderings, Annals of Pure and Applied Logic, vol. 52 (1991), pp. 39--64.
B. Khoussainov and R.A. Shore, Effective model theory: The number of models and their complexity, Models and computability: Invited papers from Logic Colloquium '97 (S.B. Cooper and J.K. Truss, editors), LMSLNS, vol. 259, Cambridge University Press, Cambridge, 1999, pp. 193--240.
N. Kogabaev, O. Kudinov, and R.G. Miller, The computable dimension of $I$-trees of infinite height, Algebra and Logic, vol. 43 (2004), no. 6, pp. 393--407.
L. Kronecker, Grundzüge einer arithmetischen Theorie der algebraischen Größ en, Journal für die reine und angewandte Mathematik, vol. 92 (1882), pp. 1--122.
S. Lempp, C. McCoy, R.G. Miller, and R. Solomon, Computable categoricity of trees of finite height, Journal of Symbolic Logic, vol. 70 (2005), pp. 151--215.
R.G. Miller, The $\Delta^0_2$-spectrum of a linear order, Journal of Symbolic Logic, vol. 66 (2001), pp. 470--486.
--------, The computable dimension of trees of infinite height, Journal of Symbolic Logic, vol. 70 (2005), pp. 111--141.
R.G. Miller and H. Schoutens, Computably categorical fields via Fermat's Last Theorem, to appear.
G. Metakides A. Nerode, Effective content of field theory, Annals of Mathematical Logic, vol. 17 (1979), pp. 289--320.
Mathematical Reviews (MathSciNet):
MR556895
M. Rabin, Computable algebra, general theory, and theory of computable fields, Transactions of the American Mathematical Society, vol. 95 (1960), pp. 341--360.
Mathematical Reviews (MathSciNet):
MR113807
J.B. Remmel, Recursive isomorphism types of recursive Boolean algebras, Journal of Symbolic Logic, vol. 46 (1981), pp. 572--594.
Mathematical Reviews (MathSciNet):
MR627907
--------, Recursively categorical linear orderings, Proceedings of the American Mathematical Society, vol. 83 (1981), pp. 387--391.
Mathematical Reviews (MathSciNet):
MR624937
L.J. Richter, Degrees of structures, Journal of Symbolic Logic, vol. 46 (1981), pp. 723--731.
Mathematical Reviews (MathSciNet):
MR641486
R.I. Soare, Recursively enumerable sets and degrees, Springer-Verlag, New York, 1987.
Mathematical Reviews (MathSciNet):
MR882921
V. Stoltenberg-Hansen and J.V. Tucker, Computable rings and fields, Handbook of computability theory (E.R. Griffor, editor), Elsevier, Amsterdam, 1999, pp. 363--447.
Y.G. Ventsov, Effective choice for relations and reducibilities in classes of constructive and positive models, Algebra and Logic, vol. 31 (1992), pp. 63--73.
B.L. van der Waerden, Algebra, vol. I, Springer-Verlag, New York, 1970, trans. F. Blum and J.R. Schulenberger.