Abstract
Let χ be the minimum cardinality of a subset of ω2 that cannot be made convergent by multiplication with a single Toeplitz matrix. By an application of a creature forcing we show that S-fraktur sign < χ is consistent. We thus answer a question by Vojtáš. We give two kinds of models for the strict inequality. The first is the combination of an א2-iteration of some proper forcing with adding א1 random reals. The second kind of models is obtained by adding δ random reals to a model of MA<κ for some δ ∈ [א1, κ). It was a conjecture of Blass that S-fraktur sign = א 1 < χ = κ holds in such a model. For the analysis of the second model we again use the creature forcing from the first model.
Original language | English |
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Pages (from-to) | 167-176 |
Number of pages | 10 |
Journal | Fundamenta Mathematicae |
Volume | 171 |
Issue number | 2 |
DOIs | |
State | Published - 2002 |
Externally published | Yes |