English

{\alpha} degrees as an automorphism base for the {\alpha}-enumeration degrees

Logic 2019-02-13 v2

Abstract

Selman's Theorem in classical Computability Theory gives a characterization of the enumeration reducibility for arbitrary sets in terms of the enumeration reducibility on the total sets: AeB    X[XeXXBeXX    AeX.X]A \le_e B \iff \forall X [X \equiv_{e} X \oplus \overline{X} \land B \le_{e} X \oplus \overline{X} \implies A \le_{e} X \oplus. \overline{X} ]. This theorem implies directly that the Turing degrees are an automorphism base of the enumeration degrees. We lift the classical proof to the setting of the α\alpha-Computability Theory to obtain the full generalization when α\alpha is a regular cardinal and partial results for a general admissible ordinal α\alpha.

Keywords

Cite

@article{arxiv.1812.11308,
  title  = {{\alpha} degrees as an automorphism base for the {\alpha}-enumeration degrees},
  author = {Dávid Natingga},
  journal= {arXiv preprint arXiv:1812.11308},
  year   = {2019}
}

Comments

8 pages

R2 v1 2026-06-23T06:58:38.056Z