Low$_2$ computably enumerable sets have hyperhypersimple supersets
Logic
2025-10-15 v3
Abstract
A longstanding question is to characterize the lattice of supersets (modulo finite sets), , of a low computably enumerable (c.e.) set. The conjecture is that . In spite of claims in the literature, this longstanding question/conjecture remains open. We contribute to this problem by solving one of the main test cases. We show that if c.e.\ is low then has an atomless hyperhypersimple superset. In fact, if is c.e.\ and low, then for any -Boolean algebra~ there is some c.e.\ such that .
Keywords
Cite
@article{arxiv.2412.01939,
title = {Low$_2$ computably enumerable sets have hyperhypersimple supersets},
author = {Peter Cholak and Rodney Downey and Noam Greenberg},
journal= {arXiv preprint arXiv:2412.01939},
year = {2025}
}
Comments
Revised due to referee's comments. Thanks!