English

A tractable case of the Turing automorphism problem: bi-uniformly $E_0$-invariant Cantor homeomorphisms

Logic 2020-09-01 v2

Abstract

A function F:2ω2ωF:2^\omega\to 2^\omega is an E0E_0-isomorphism if for all x,y2ωx,y\in 2^\omega, we have xE0y    f(x)E0f(y)xE_0y\iff f(x)E_0 f(y), where xE0y    (a)(nb)x(n)=y(n)xE_0y\iff(\exists a)(\forall n\ge b) x(n)=y(n). If such witnesses aa for xE0yxE_0 y and for f(x)E0f(y)f(x)E_0 f(y) depend on each other but not on xx, yy, then FF is called bi-uniform. It is shown that a homeomorphism of Cantor space which is a bi-uniform E0E_0-isomorphism can induce only the trivial automorphism of the Turing degrees.

Keywords

Cite

@article{arxiv.1908.05381,
  title  = {A tractable case of the Turing automorphism problem: bi-uniformly $E_0$-invariant Cantor homeomorphisms},
  author = {Bjørn Kjos-Hanssen},
  journal= {arXiv preprint arXiv:1908.05381},
  year   = {2020}
}

Comments

Accepted for publication in: Higher recursion theory and set theory. Lecture Notes Series, Institute of Mathematical Sciences, National University of Singapore, World Scientific Publishing, Hackensack, NJ