English

Pseudojump inversion in special r. b. $\Pi^0_1$ classes

Logic 2021-02-12 v1

Abstract

The Jump Inversion Theorem says that for every real AT0A \ge_T 0' there is a real BB such that ATBTB0A \equiv_T B' \equiv_T B \oplus 0'. A known refinement of this theorem says that we can choose BB to be a member of any special Π10\Pi^0_1 subclass of {0,1}ω\{0,1\}^\omega. We now consider the possibility of analogous refinements of two other well-known theorems: the Join Theorem -- for all reals AA and ZZ such that ATZ0A \ge_T Z \oplus 0' and Z>T0Z >_T 0, there is a real BB such that ATBTB0TBZA \equiv_T B' \equiv_T B \oplus 0' \equiv_T B \oplus Z -- and the Pseudojump Inversion Theorem -- for all reals AT0A \ge_T 0' and every eωe \in \omega, there is a real BB such that ATBWeBTB0A \equiv_T B \oplus W_e^B \equiv_T B \oplus 0'. We show that in these theorems, BB can be found in some special Π10\Pi^0_1 subclasses of {0,1}ω\{0,1\}^\omega but not in others.

Cite

@article{arxiv.2102.06135,
  title  = {Pseudojump inversion in special r. b. $\Pi^0_1$ classes},
  author = {Hayden R. Jananthan and Stephen G. Simpson},
  journal= {arXiv preprint arXiv:2102.06135},
  year   = {2021}
}

Comments

19 pages, submitted for publication

R2 v1 2026-06-23T23:04:39.195Z