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Minimal Weak Truth Table Degrees and Computably Enumerable Turing Degrees

About this Title

Rodney G. Downey, School of Mathematics, Statistics and Operations Research, Victoria University of Wellington, Wellington, New Zealand, Keng Meng Ng, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore and Reed Solomon, Department of Mathematics, University of Connecticut, Storrs, CT 06268, USA

Publication: Memoirs of the American Mathematical Society
Publication Year: 2020; Volume 265, Number 1284
ISBNs: 978-1-4704-4162-3 (print); 978-1-4704-6136-2 (online)
DOI: https://doi.org/10.1090/memo/1284
Published electronically: April 6, 2020
Keywords: Computably enumerable set, Turing degree, weak truth table degree, minimal degree
MSC: Primary 03D25; Secondary 03D28, 03D30

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Table of Contents

Chapters

  • 1. Introduction
  • 2. Informal Construction
  • 3. Formal Construction
  • 4. Limiting Results

Abstract

Two of the central concepts for the study of degree structures in computability theory are computably enumerable degrees and minimal degrees. For strong notions of reducibility, such as $m$-deducibility or truth table reducibility, it is possible for computably enumerable degrees to be minimal. For weaker notions of reducibility, such as weak truth table reducibility or Turing reducibility, it is not possible to combine these properties in a single degree. We consider how minimal weak truth table degrees interact with computably enumerable Turing degrees and obtain three main results. First, there are sets with minimal weak truth table degree which bound noncomputable computably enumerable sets under Turing reducibility. Second, no set with computable enumerable Turing degree can have minimal weak truth table degree. Third, no $\Delta ^0_2$ set which Turing bounds a promptly simple set can have minimal weak truth table degree.

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