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Intersections of ℓp spaces in the Borel hierarchy
Journal of Mathematical Analysis and Applications ( IF 1.2 ) Pub Date : 2021-01-12 , DOI: 10.1016/j.jmaa.2021.124922 Vassilios Gregoriades
中文翻译:
的交叉口ℓ p在博雷尔层次空间
更新日期:2021-01-16
Journal of Mathematical Analysis and Applications ( IF 1.2 ) Pub Date : 2021-01-12 , DOI: 10.1016/j.jmaa.2021.124922 Vassilios Gregoriades
We show that if Y is one of the spaces , , or where , and if the F-space is contained in Y properly (), then first shows up in the Borel hierarchy of Y at the multiplicative class of the third level. In particular is neither an nor a subset of Y. This answers a question by Nestoridis. This result provides a natural example of a set in the third level of the Borel hierarchy and with its help we also give some examples in the fourth level.
中文翻译:
的交叉口ℓ p在博雷尔层次空间
我们证明如果Y是空格之一, , 要么 哪里 ,以及F空间 正确包含在Y中(), 然后 首先出现在Y的Borel层次中的第三级乘法类中。特别是 既不是 也不是 Y的子集。这回答了Nestoridis的问题。此结果提供了Borel层次结构第三层中的集合的自然示例,在其帮助下,我们还给出了第四层中的一些示例。