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Forcing closed unbounded subsets of ω2

✍ Scribed by M.C. Stanley

Publisher
Elsevier Science
Year
2001
Tongue
English
Weight
459 KB
Volume
110
Category
Article
ISSN
0168-0072

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✦ Synopsis

It is shown that there is no satisfactory ÿrst-order characterization of those subsets of !2 that have closed unbounded subsets in !1; !2 and GCH preserving outer models. These "anticharacterization" results generalize to subsets of successors of uncountable regular cardinals. Similar results are proved for trees of height and cardinality Ä + and for partitions of [Ä + ] 2 , when Ä is an inÿnite cardinal.

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