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The undecidability of simultaneous rigid E-unification with two variables

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Computational Logic and Proof Theory (KGC 1997)

Part of the book series: Lecture Notes in Computer Science ((LNCS,volume 1289))

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Abstract

Recently it was proved that the problem of simultaneous rigid E-unification, or SREU, is undecidable. Here we show that 4 rigid equations with ground left-hand sides and 2 variables already imply undecidability. As a corollary we improve the undecidability result of the 3*-fragment of intuitionistic logic with equality. Our proof shows undecidability of a very restricted subset of the 33-fragment. Together with other results, it contributes to a complete characterization of decidability of the prenex fragment of intuitionistic logic with equality, in terms of the quantifier prefix.

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Authors and Affiliations

  1. Uppsala University Computing Science Department, P.O. Box 311, S-751 05, Uppsala, Sweden

    Margus Veanes

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  1. Margus Veanes
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Georg Gottlob Alexander Leitsch Daniele Mundici

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© 1997 Springer-Verlag Berlin Heidelberg

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Veanes, M. (1997). The undecidability of simultaneous rigid E-unification with two variables. In: Gottlob, G., Leitsch, A., Mundici, D. (eds) Computational Logic and Proof Theory. KGC 1997. Lecture Notes in Computer Science, vol 1289. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-63385-5_52

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  • DOI: https://doi.org/10.1007/3-540-63385-5_52

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  • Print ISBN: 978-3-540-63385-3

  • Online ISBN: 978-3-540-69806-7

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