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Σ2-induction and the construction of a high degree

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Recursion Theory Week

Part of the book series: Lecture Notes in Mathematics ((LNM,volume 1432))

Abstract

We show that the subsystem of Peano Arithmetic containing only induction for Σ2 formulas suffices to prove the existence of a recursively enumerable set of high, incomplete degree. By a result of Mytilinaios and Slaman, bounding for Σ2 formulas does not suffice to prove that such a set exists. In contrast, by a result of Groszek and Slaman, induction for Σ1 formulas suffices to carry out any Friedberg-style finite injury priority argument.

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References

  1. Enderton, H. B., A Mathematical Introduction to Logic, Academic Press, New York, 1972.

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Klaus Ambos-Spies Gert H. Müller Gerald E. Sacks

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© 1990 Springer-Verlag

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Groszek, M., Mytilinaios, M. (1990). Σ2-induction and the construction of a high degree. In: Ambos-Spies, K., Müller, G.H., Sacks, G.E. (eds) Recursion Theory Week. Lecture Notes in Mathematics, vol 1432. Springer, Berlin, Heidelberg. https://doi.org/10.1007/BFb0086119

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  • DOI: https://doi.org/10.1007/BFb0086119

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  • Publisher Name: Springer, Berlin, Heidelberg

  • Print ISBN: 978-3-540-52772-5

  • Online ISBN: 978-3-540-47142-4

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