Combinatorial properties of MAD families
Abstract
We study some strong combinatorial properties of $\textsf{MAD}$ families. An ideal $\mathcal{I}$ is Shelah-Steprāns if for every set $X\subseteq{\left[ \omega\right]}^{<\omega}$ there is an element of $\mathcal{I}$ that either intersects every set in $X$ or contains infinitely many members of it. We prove that a Borel ideal is Shelah-Steprāns if and only if it is Katětov above the ideal $\textsf{fin}\times\textsf{fin}$. We prove that Shelah-Steprāns $\textsf{MAD}$ families have strong indestructibility properties (in particular, they are both Cohen and random indestructible). We also consider some other strong combinatorial properties of $\textsf{MAD}$ families. Finally, it is proved that it is consistent to have $\mathrm{non}(\mathcal{M}) = {\aleph}_{1}$ and no Shelah-Steprāns families of size ${\aleph}_{1}$.
- Publication:
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arXiv e-prints
- Pub Date:
- June 2022
- DOI:
- arXiv:
- arXiv:2206.14936
- Bibcode:
- 2022arXiv220614936B
- Keywords:
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- Mathematics - Logic;
- Mathematics - General Topology
- E-Print:
- 43 pages. Submitted. arXiv admin note: text overlap with arXiv:1810.09680