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Classes defined by stars and neighbourhood assignments

机译:由星级和邻里分配定义的类

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We apply and develop an idea of E. van Douwen used to define D-spaces. Given a topological property P, the class P~* dual to P (with respect to neighbourhood assignments) consists of spaces X such that for any neighbourhood assignment {O_x: x ∈ X} there is Y is contained in X with Y ∈ P and ∪{O_x: x ∈ Y} = X. We prove that the classes of compact, countably compact and pseudocompact are self-dual with respect to neighbourhood assignments. It is also established that all spaces dual to hereditarily Lindeloef spaces are Lindeloef. In the second part of this paper we study some non-trivial classes of pseudocompact spaces defined in an analogous way using stars of open covers instead of neighbourhood assignments.
机译:我们应用并发展了一种用于定义D空间的E. van Douwen的想法。给定一个拓扑属性P,对P对偶的类P〜*(关于邻域分配)由空间X组成,这样对于任何邻域分配{O_x:x∈X},Y中的Y都包含Y∈P和∪{O_x:x∈Y} =X。我们证明了紧致,可数紧致和伪紧致的类别在邻域分配方面是对偶的。还可以确定,所有遗传上Lindeloef空间对偶的空间都是Lindeloef。在本文的第二部分中,我们研究了一些非平凡的伪紧致空间类别,这些类别以类似的方式使用敞开的星形而不是邻域分配来定义。

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