<p>We investigate degree structures induced by computable reducibility ≤<sub>c</sub> on binary relations having domain ω. We prove that for each of the following structures induced by ≤<sub>c</sub>, its first-order theory is recursively isomorphic to the second-order arithmetic: the structure <b>Pr</b> of all preorders, and the structure <b>LP</b> of all linear preorders.</p>

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The Structure of Computable Reducibility on Preorders

  • D. B. Alish,
  • N. A. Bazhenov

摘要

We investigate degree structures induced by computable reducibility ≤c on binary relations having domain ω. We prove that for each of the following structures induced by ≤c, its first-order theory is recursively isomorphic to the second-order arithmetic: the structure Pr of all preorders, and the structure LP of all linear preorders.