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

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

• Type: Conference
• Year: 2007
• Where: FSTTCS
• Authors: Pierre Chambart, Ph. Schnoebelen
• Keywords: FSTTCS 2007, Post Embedding Problem, Primitive Recursive, Subword Relation