Initial segments of the degrees of size א1

Uri Abraham, Richard A. Shore

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


We settle a series of questions first raised by Yates at the Jerusalem (1968) Colloquium on Mathematical Logic by characterizing the initial segments of the degrees of unsolvability of size א1: Every upper semi-lattice of size א1 with zero, in which every element has at most countably many predecessors, is isomorphic to an initial segment of the Turing degrees.

Original languageEnglish
Pages (from-to)1-51
Number of pages51
JournalIsrael Journal of Mathematics
Issue number1
StatePublished - 1 Feb 1986

ASJC Scopus subject areas

  • General Mathematics


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