English

Computably Enumerable Sets that are Automorphic to Low Sets

Logic 2015-12-29 v2

Abstract

We work with the structure consisting of all computably enumerable (c.e.) sets ordered by set inclusion. The question we will partially address is which c.e.\ sets are autormorphic to low (or low2_2 sets. Using work of Miller, we can see that every set with semilow complement is Δ30\Delta^0_3 automorphic to a low set. While it remains open whether every set with semilow complement is effectively automorphic to a low set, we show that there are sets without semilow complement that are effectively automorphic to low sets. We also consider other lowness notions such as having a semilow1.5_{1.5} complement, having the the outer splitting property, and having a semilow2_2 complement. We show that in every non low \ce degree, there are sets with semilow1.5_{1.5} complements without semilow complements as well as sets with semilow2_2 complements and the outer splitting property that do not have semilow1.5_{1.5} complements. We also address the question of which sets are automorphic to low2_2 sets.

Keywords

Cite

@article{arxiv.1510.04199,
  title  = {Computably Enumerable Sets that are Automorphic to Low Sets},
  author = {Peter Cholak and Rachel Epstein},
  journal= {arXiv preprint arXiv:1510.04199},
  year   = {2015}
}

Comments

Submitted. In this version we make a number of corrections

R2 v1 2026-06-22T11:20:23.098Z