The σ-ideal generated by H-sets∗
نویسنده
چکیده
It is consistent with the axioms of set theory that the circle T can be covered by א1 many closed sets of uniqueness while a much larger number of H-sets is necessary to cover it. In the proof of this theorem, the descriptive set theoretic phenomenon of overspill appears, and it is reformulated as a natural forcing preservation principle that persists through the operation of countable support product.
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