Post Embedding Problem Is Not Primitive Recursive, with Applications to Channel Systems

  • Pierre Chambart
  • Philippe Schnoebelen
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4855)


We introduce PEP, the Post Embedding Problem, a variant of PCP where one compares strings with the subword relation, and PEP reg, a further variant where solutions are constrained and must belong to a given regular language. PEP reg is decidable but not primitive recursive. This entails the decidability of reachability for unidirectional systems with one reliable and one lossy channel.


Post correspondence problem Lossy channel systems Higman’s Lemma 


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Copyright information

© Springer-Verlag Berlin Heidelberg 2007

Authors and Affiliations

  • Pierre Chambart
    • 1
  • Philippe Schnoebelen
    • 1
  1. 1.LSV, ENS Cachan, CNRS, 61, av. Pdt. Wilson, F-94230 CachanFrance

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