当前位置:
X-MOL 学术
›
J. Symb. Log.
›
论文详情
Our official English website, www.x-mol.net, welcomes your
feedback! (Note: you will need to create a separate account there.)
RESTRICTED MAD FAMILIES
The Journal of Symbolic Logic ( IF 0.5 ) Pub Date : 2019-11-05 , DOI: 10.1017/jsl.2019.76 OSVALDO GUZMÁN , MICHAEL HRUŠÁK , OSVALDO TÉLLEZ
The Journal of Symbolic Logic ( IF 0.5 ) Pub Date : 2019-11-05 , DOI: 10.1017/jsl.2019.76 OSVALDO GUZMÁN , MICHAEL HRUŠÁK , OSVALDO TÉLLEZ
Let ${\cal I}$ be an ideal on ω . By cov${}_{}^{\rm{*}}({\cal I})$ we denote the least size of a family ${\cal B} \subseteq {\cal I}$ such that for every infinite $X \in {\cal I}$ there is $B \in {\cal B}$ for which $B\mathop \cap \nolimits X$ is infinite. We say that an AD family ${\cal A} \subseteq {\cal I}$ is a MAD family restricted to ${\cal I}$ if for every infinite $X \in {\cal I}$ there is $A \in {\cal A}$ such that $|X\mathop \cap \nolimits A| = \omega$ . Let a$\left( {\cal I} \right)$ be the least size of an infinite MAD family restricted to ${\cal I}$ . We prove that If $max$ {a,cov${}_{}^{\rm{*}}({\cal I})\}$ then a$\left( {\cal I} \right) = {\omega _1}$ , and consequently, if ${\cal I}$ is tall and $\le {\omega _2}$ then a$\left( {\cal I} \right) = max$ {a,cov${}_{}^{\rm{*}}({\cal I})\}$ . We use these results to prove that if c$\le {\omega _2}$ then o$= \overline o$ and that as $= max$ {a,non$({\cal M})\}$ . We also analyze the problem whether it is consistent with the negation of CH that every AD family of size ω 1 can be extended to a MAD family of size ω 1 .
中文翻译:
受限制的疯狂家庭
让${\卡尔我}$ 成为一个理想的人ω . 由 cov${}_{}^{\rm{*}}({\cal I})$ 我们表示一个家庭的最小规模${\cal B} \subseteq {\cal I}$ 这样对于每一个无限$X \in {\cal I}$ 有$B \in {\cal B}$ 为此$B\mathop \cap \nolimits X$ 是无限的。我们说一个AD家族${\cal A} \subseteq {\cal I}$ 是一个MAD 家族仅限于 ${\卡尔我}$ 如果对于每个无限$X \in {\cal I}$ 有$A \in {\cal A}$ 这样$|X\mathop \cap \nolimits A| = \欧米茄$ . 让一个$\left( {\cal I} \right)$ 是无限 MAD 家族的最小规模,限制为${\卡尔我}$ . 我们证明如果$最大$ {a,cov${}_{}^{\rm{*}}({\cal I})\}$ 然后一个$\left( {\cal I} \right) = {\omega _1}$ ,因此,如果${\卡尔我}$ 很高,而且$\le {\omega _2}$ 然后一个$\left( {\cal I} \right) = max$ {a,cov${}_{}^{\rm{*}}({\cal I})\}$ . 我们用这些结果来证明如果 c$\le {\omega _2}$ 然后$= \overline o$ 那一个s $= 最大值$ {一个,非$({\cal M})\}$ . 我们还分析了每个AD家族的大小是否与CH的否定一致的问题ω 1 可以扩展到 MAD 系列的大小ω 1 .
更新日期:2019-11-05
中文翻译:
受限制的疯狂家庭
让