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New proof for the undecidability of the circular PCP

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Abstract

We give simpler proof for the undecidability of the circular Post Correspondence Problem that was originally proved undecidable by Ruohonen (Acta Informatica 19:357–367, 1983). The key feature of our proof is the undecidability of the word problem of special semi-Thue systems where derivations are deterministic and reversible for words containing a single occurrence of a letter from a given set.

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Acknowledgments

We thank the anonymous referee for useful comments.

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Authors and Affiliations

  1. Department of Mathematics and Statistics, University of Turku, FI-20014 , Turku, Finland

    Vesa Halava & Tero Harju

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  1. Vesa Halava
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  2. Tero Harju
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Correspondence to Vesa Halava.

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Halava, V., Harju, T. New proof for the undecidability of the circular PCP. Acta Informatica 50, 331–341 (2013). https://doi.org/10.1007/s00236-013-0183-5

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  • DOI: https://doi.org/10.1007/s00236-013-0183-5

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