- Tytuł:
- Borel sets with large squares
- Autorzy:
- Shelah, Saharon
- Powiązania:
- https://bibliotekanauki.pl/articles/1205277.pdf
- Data publikacji:
- 1999
- Wydawca:
- Polska Akademia Nauk. Instytut Matematyczny PAN
- Opis:
-
For a cardinal μ we give a sufficient condition $⊕_μ$ (involving ranks measuring existence of independent sets) for:
$⊗_μ$ if a Borel set B ⊆ ℝ × ℝ contains a μ-square (i.e. a set of the form A × A with |A| =μ) then it contains a $2^{ℵ_0}$-square and even a perfect square,
and also for
$⊗'_μ$ if $ψ ∈ L_{ω_1, ω}$ has a model of cardinality μ then it has a model of cardinality continuum generated in a "nice", "absolute" way.
Assuming $MA + 2^{ℵ_0} > μ$ for transparency, those three conditions ($⊕_μ$, $⊗_μ$ and $⊗'_μ$) are
equivalent, and from this we deduce that e.g. $∧_{α < ω_1}[ 2^{ℵ_0}≥ ℵ_α ⇒ ¬ ⊗_{ℵ_α}]$, and also that
$min{μ: ⊗_μ}$, if $ < 2^{ℵ_0}$, has cofinality $ℵ_1$.
We also deal with Borel rectangles and related model-theoretic problems. - Źródło:
-
Fundamenta Mathematicae; 1999, 159, 1; 1-50
0016-2736 - Pojawia się w:
- Fundamenta Mathematicae
- Dostawca treści:
- Biblioteka Nauki