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Cardinal invariants of Haar null and Haar meager sets
Proceedings of the Royal Society of Edinburgh Section A: Mathematics ( IF 1.3 ) Pub Date : 2020-10-27 , DOI: 10.1017/prm.2020.73 Márton Elekes , Márk Poór
Proceedings of the Royal Society of Edinburgh Section A: Mathematics ( IF 1.3 ) Pub Date : 2020-10-27 , DOI: 10.1017/prm.2020.73 Márton Elekes , Márk Poór
A subset X of a Polish group G is Haar null if there exists a Borel probability measure μ and a Borel set B containing X such that μ(gBh ) = 0 for every g , h ∈ G . A set X is Haar meager if there exists a compact metric space K , a continuous function f : K → G and a Borel set B containing X such that f −1 (gBh ) is meager in K for every g , h ∈ G . We calculate (in ZFC ) the four cardinal invariants (add, cov, non, cof) of these two σ-ideals for the simplest non-locally compact Polish group, namely in the case $G = \mathbb {Z}^\omega$ . In fact, most results work for separable Banach spaces as well, and many results work for Polish groups admitting a two-sided invariant metric. This answers a question of the first named author and Vidnyánszky.
中文翻译:
Haar null 和 Haar 微薄集的基数不变量
一个子集X 一个波兰团体G 是哈尔空 如果存在一个 Borel 概率测度 μ 和一个 Borel 集乙 包含X 使得 μ(gBh ) = 0 对于每个G ,H ∈G . 一套X 是哈尔微薄 如果存在紧度量空间ķ , 一个连续函数F :ķ →G 和一个 Borel 集乙 包含X 这样F -1 (gBh ) 是微薄的ķ 对于每个G ,H ∈G . 我们计算(在ZFC ) 这两个 σ-理想的四个基本不变量(add, cov, non, cof)对于最简单的非局部紧波兰群,即在这种情况下$G = \mathbb {Z}^\omega$ . 事实上,大多数结果也适用于可分离的 Banach 空间,并且许多结果适用于承认双边不变度量的波兰团体。这回答了第一作者和 Vidnyánszky 的问题。
更新日期:2020-10-27
中文翻译:
Haar null 和 Haar 微薄集的基数不变量
一个子集