Bourbaki

Exercise 28, § 9

General Topology, I, 149

a) Let KK be the discrete space {0,1}\{0, 1\}. If XX is any compact space, let FF be the set of mappings ff of KK into the set F(X)\mathfrak{F}(X) of closed subsets of XX such that X=f(0)∪f(1)X = f(0) \cup f(1). Consider the compact space Y=KFY = K^F; show that for each y=(yf)f∈Fy = (y_f)_{f \in F} in YY, the intersection of the closed sets f(yf)f(y_f) of XX consists of at most one point. The set ZZ of y∈Yy \in Y for which this intersection is not empty is a closed subset of YY. If φ(y)\varphi(y) is the unique point common to the f(yf)f(y_f) for y∈Zy \in Z, show that φ\varphi is a continuous surjection of ZZ onto XX.

b) Give an example of a compact space XX such that there is no surjective continuous mapping of a compact space of the form KAK^A onto XX [use Exercise 4 b) of § 4 and Exercise 26 of § 9].

Solution

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