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arXiv math/9211202math.LO
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Hechler强迫的组合性质

Combinatorial properties of Hechler forcing

Jörg Brendle, Haim Judah, Saharon Shelah

摘要:

在这项工作中,我们使用的概念排名第一介绍詹姆斯鲍姆加特纳和彼得Dordal和后来独立开发的第三作者表明,增加一个Hechler真正有很强的组合后果。我们证明:1)假设ω_1^V = ω_1^L,V[d]中没有实数最终不同于L[d]中的实数,其中d是V上的Hechler; 2)增加一个Hechler实数使得Cicho 'n图左侧的不变量等于ω_1,右侧的不变量等于2 ^ω,并产生大小为ω_1的ω子集的最大几乎不相交族; 3)在V[r][d]中不存在V上随机实数的完满集,其中r是V上的随机数,d是V[r]上的Hechler,从而回答了第一和第二作者的一个问题。作为证明3)的中间步骤,我们证明了给定模型M是ZFC的子集N,使得在M上的N中存在随机实的完满集,或者在M上的N中存在支配实,或者在N中mu(2 Ω cap M)= 0。

英文摘要:

In this work we use a notion of rank first introduced by James Baumgartner and Peter Dordal and later developed independently by the third author to show that adding a Hechler real has strong combinatorial consequences. We prove: 1) assuming omega_1^V = omega_1^L, there is no real in V[d] which is eventually different from the reals in L[d], where d is Hechler over V; 2) adding one Hechler real makes the invariants on the left-hand side of Cicho'n's diagram equal omega_1 and those on the right-hand side equal 2^omega and produces a maximal almost disjoint family of subsets of omega of size omega_1; 3) there is no perfect set of random reals over V in V[r][d], where r is random over V and d Hechler over V[r], thus answering a question of the first and second authors. As an intermediate step in the proof of 3) we show that given models M subseteq N of ZFC such that there is a perfect set of random reals in N over M, either there is a dominating real in N over M or mu (2^omega cap M) = 0 in N.

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