Universal computably enumerable sets and initial segment prefix-free complexity

  • Authors:
  • George Barmpalias

  • Affiliations:
  • -

  • Venue:
  • Information and Computation
  • Year:
  • 2013

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Abstract

We show that there are Turing complete computably enumerable sets of arbitrarily low nontrivial initial segment prefix-free complexity. In particular, given any computably enumerable set A with nontrivial prefix-free initial segment complexity, there exists a Turing complete computably enumerable set B with complexity strictly less than the complexity of A. On the other hand it is known that sets with trivial initial segment prefix-free complexity are not Turing complete. Moreover we give a generalization of this result for any finite collection of computably enumerable sets A"i, i