Abstract
Three types of “primitive” or “prime” solutions for PCP have earlier been investigated. The sets of words belonging to one of the three types (for some instance of PCP) form an increasing hierarchy. In our main result we show that the hierarchy is proper, except the binary case. We also give a sharpened characterization of the finite type.
Work supported by Project 11281 of the Academy of Finland
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© 1995 Springer-Verlag Berlin Heidelberg
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Lipponen, M. (1995). Post correspondence problem: Words possible as primitive solutions. In: Fülöp, Z., Gécseg, F. (eds) Automata, Languages and Programming. ICALP 1995. Lecture Notes in Computer Science, vol 944. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-60084-1_63
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DOI: https://doi.org/10.1007/3-540-60084-1_63
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