Combinatorial properties of MAD families
Logic
2026-01-14 v1 General Topology
Abstract
We study some strong combinatorial properties of families. An ideal is Shelah-Stepr\={a}ns if for every set there is an element of that either intersects every set in or contains infinitely many members of it. We prove that a Borel ideal is Shelah-Stepr\={a}ns if and only if it is Kat\v{e}tov above the ideal . We prove that Shelah-Stepr\={a}ns families have strong indestructibility properties (in particular, they are both Cohen and random indestructible). We also consider some other strong combinatorial properties of families. Finally, it is proved that it is consistent to have and no Shelah-Stepr\={a}ns families of size .
Keywords
Cite
@article{arxiv.2206.14936,
title = {Combinatorial properties of MAD families},
author = {Jörg Brendle and Osvaldo Guzmán and Michael Hrušák and Dilip Raghavan},
journal= {arXiv preprint arXiv:2206.14936},
year = {2026}
}
Comments
43 pages. Submitted. arXiv admin note: text overlap with arXiv:1810.09680