Bourbaki

Exercise 29, § 9

General Topology, I, p. 110

(a) Let K be the discrete space {0,1}\{0, 1\}. For every compact space X, let F be the set of mappings ff from K into the set F(X)\mathfrak{F}(X) of closed subsets of X, such that X=f(0)∪f(1)X = f(0) \cup f(1). Consider the compact space Y=KFY = K^F; now prove that for every y=(yf)f∈Fy = (y_f)_{f \in F} in Y, the intersection of the closed sets f(yf)f(y_f) of X is empty or reduced to one point. The subset Z of the y∈Yy \in Y such that this intersection is not empty is a closed subset of Y; if φ(y)\varphi(y) is the unique common point of the f(yf)f(y_f) for y∈Zy \in Z, now prove that φ\varphi is a continuous surjective mapping from Z onto X.

(b) Give an example of a compact space X such that there exists no continuous surjective mapping from a compact space of the form KAK^A onto X (use exerc. 4 b) of I, p. 95 and exerc. 27 of I, p. 110).

Solution

No solution has been written yet.

Machine translation of the English, by gpt-5-mini. Not checked by a person. That model is a cut down version of the one the rest of this language was written by.