Abstract
Two families A,B of subsets of ω are said to be separated if there is a subset of ω which mod finite contains every member of A and is almost disjoint from every member of B. If A and B are countable disjoint subsets of an almost disjoint family, then they are separated. Luzin gaps are well-known examples of ω1-sized subfamilies of an almost disjoint family which can not be separated. An almost disjoint family will be said to be ω1-separated if any disjoint pair of ≤ω1-sized subsets are separated. It is known that the proper forcing axiom (PFA) implies that no maximal almost disjoint family is ≤ω1-separated. We prove that this does not follow from Martin's Axiom.
| Original language | English |
|---|---|
| Pages (from-to) | 107-115 |
| Number of pages | 9 |
| Journal | Rendiconti del Circolo Matematico di Palermo |
| Volume | 61 |
| Issue number | 1 |
| DOIs | |
| State | Published - Apr 2012 |
Keywords
- Martin's Axiom
- Maximal almost disjoint family
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