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arXiv math/0310438math.LO
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具有特性的超滤器

Ultrafilters with property (s)

Arnold W. Miller

摘要:

集合X是康托尔集的子集,它具有性质(Marczewski(Spzilrajn))当且仅当对每个完满集P,存在包含在P中的完满集Q,使得Q是X的子集或Q与X不相交。设U是Ω上的非主超滤子。不难看出,如果U被萨克斯强迫保留,即,它在泛型扩张中用完美集的偏序强制生成一个超滤子,则U在基模型中具有性质.已知Sacks强迫保持选择性超滤子甚至P点。另一方面(回答Hrusak提出的一个问题),我们表明,假设CH(或更一般的MA为ctble偏序集)存在一个超滤子U的性质(S),使U不产生超滤子在任何扩展,增加了一个新的子集的欧米茄。http://www.math.wisc.edu/~miller/res/index.htmlmiller@math.wisc.edu

英文摘要:

A set X which is a subset of the Cantor set has property (s) (Marczewski (Spzilrajn)) iff for every perfect set P there exists a perfect set Q contained in P such that Q is a subset of X or Q is disjoint from X. Suppose U is a nonprincipal ultrafilter on omega. It is not difficult to see that if U is preserved by Sacks forcing, i.e., it generates an ultrafilter in the generic extension after forcing with the partial order of perfect sets, then U has property (s) in the ground model. It is known that selective ultrafilters or even P-points are preserved by Sacks forcing. On the other hand (answering a question raised by Hrusak) we show that assuming CH (or more generally MA for ctble posets) there exists an ultrafilter U with property (s) such that U does not generate an ultrafilter in any extension which adds a new subset of omega. http://www.math.wisc.edu/~miller/res/index.html miller@math.wisc.edu

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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