The comparability numbers and the incomparability numbers
Logic
2026-01-30 v2
Abstract
We introduce new cardinal invariants of a poset, called the comparability number and the incomparability number. We determine their value for well-known posets, such as , , the Turing degrees , the quotient algebra , the ideals and . Moreover, we consider these invariants for the Rudin-Keisler ordering of the nonprincipal ultrafilters on . We also consider these invariants for ideals on and on .
Cite
@article{arxiv.2302.08040,
title = {The comparability numbers and the incomparability numbers},
author = {Tatsuya Goto},
journal= {arXiv preprint arXiv:2302.08040},
year = {2026}
}
Comments
14 pages