Elementary differences among jump classes

  • Authors:

  • Angsheng Li

  • Affiliations:

  • State Key Laboratory of Computer Science, Institute of Software, Chinese Academy of Sciences, P.O. Box, 8718, Beijing, 100190, PR China

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2009

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Abstract

It is shown that Th(H"1)Th(H"n) holds for every n1, where H"m is the upper semi-lattice of all high"m computably enumerable (c.e.) degrees for m0, giving a first elementary difference among the highness hierarchies of the c.e. degrees.