
arXiv: 1405.0191
AbstractAll spaces are assumed to be separable and metrizable. Our main result is that the statement “For every space X, every closed subset of X has the perfect set property if and only if every analytic subset of X has the perfect set property” is equivalent to b > ω1 (hence, in particular, it is independent of ZFC). This, together with a theorem of Solecki and an example of Miller, will allow us to determine the status of the statement “For every space X, if every Γ subset of X has the perfect set property then every Γ′ subset of X has the perfect set property” as Γ, Γ′ range over all pointclasses of complexity at most analytic or coanalytic.Along the way, we define and investigate a property of independent interest. We will say that a subset W of 2ω has the Grinzing property if it is uncountable and for every uncountable Y ⊆ W there exists an uncountable collection consisting of uncountable subsets of Y with pairwise disjoint closures in 2ω. The following theorems hold.(1)There exists a subset of 2ω with the Grinzing property.(2)Assume MA + ¬CH. Then 2ω has the Grinzing property.(3)Assume CH. Then 2ω does not have the Grinzing property.The first result was obtained by Miller using a theorem of Todorčević, and is needed in the proof of our main result.
101013 Mathematische Logik, General Topology (math.GN), Mathematics - Logic, 101013 Mathematical logic, Perfect set property, analytic set, Grinzing property, 101022 Topology, Metric spaces, metrizability, unbounding number, Dropping polishness, perfect set property, separable metrizable spaces, FOS: Mathematics, dropping Polishness, Unbounding number, Consistency and independence results, 101022 Topologie, 03H15, 54H05, Logic (math.LO), Descriptive set theory, Mathematics - General Topology
101013 Mathematische Logik, General Topology (math.GN), Mathematics - Logic, 101013 Mathematical logic, Perfect set property, analytic set, Grinzing property, 101022 Topology, Metric spaces, metrizability, unbounding number, Dropping polishness, perfect set property, separable metrizable spaces, FOS: Mathematics, dropping Polishness, Unbounding number, Consistency and independence results, 101022 Topologie, 03H15, 54H05, Logic (math.LO), Descriptive set theory, Mathematics - General Topology
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