Abstract
Continuing recent research of [3–9] et al. we study the composition of homomorphisms, inverse homomorphisms and twin-morphisms 〈g,h〉 and 〈g,h〉−1, where 〈g,h〉 (w) = g(w) ∩ h(w) and 〈g,h〉−1 (w) = g−1(w) ∩ h−1 (w). We investigate some properties of these morphic mappings and concentrate on a characterization of the recursively enumerable sets, which says: For every recursively enumerable set L there exist four homomorphisms such that L=f1 ° <f2, f3> ° f -14 ({$}) and L=h1 ° <h2, h3>-1 ° h -14 ({$}), and four homomorphisms are minimal for such representations.
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© 1984 Springer-Verlag Berlin Heidelberg
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Brandenburg, F.J. (1984). A truely morphic characterization of recursively enumerable sets. In: Chytil, M.P., Koubek, V. (eds) Mathematical Foundations of Computer Science 1984. MFCS 1984. Lecture Notes in Computer Science, vol 176. Springer, Berlin, Heidelberg. https://doi.org/10.1007/BFb0030300
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DOI: https://doi.org/10.1007/BFb0030300
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