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Given a space we investigate the descriptive complexity class of the set of all its closed zero-dimensional subsets, viewed as a subset of the hyperspace of all closed subsets of . We prove that and for any countable ordinal . In particular we prove that there exists a one-dimensional Polish subpace of for which is not in the smallest non trivial pointclass closed under complementation and the Souslin operation .

生成讲解博客的中文版本

生成AI智能校验的中文版本