Friedberg numberings in the Ershov hierarchy

Serikzhan A. Badaev, Mustafa Manat, Andrea Sorbi

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


We show that for every ordinal notation ξ of a nonzero computable ordinal, there exists a (formula presented)—computable family which up to equivalence has exactly one Friedberg numbering, which does not induce the least element in the corresponding Rogers semilattice.

Original languageEnglish
Pages (from-to)59-73
Number of pages15
JournalArchive for Mathematical Logic
Issue number1-2
Publication statusPublished - Jan 31 2015


  • Computable numbering
  • Friedberg numbering
  • Hierarchy of Ershov
  • Rogers semilattice

ASJC Scopus subject areas

  • Philosophy
  • Logic

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