Cardinal invariants of Haar null and Haar meager sets
Abstract
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 = Zω. 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 Z. Vidny\'anszky.
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