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On pointwise approximation of arbitrary functions by countable families of continuous functions
Authors:A B Arkhangel'skii  D B Shakhmatov
Abstract:The following problem is considered. Given a real-valued function f defined on a topological space X, when can one find a countable familyf n :n∈ω of continuous real-valued functions on X that approximates f on finite subsets of X? That is, for any finite set F?X and every real number ε>0 one can choosen∈ω such that ∥f(x)?fn(x)∥<ε for everyxF. It will be shown that the problem has a positive solution if and only if X splits. A space X is said to split if, for any A?X, there exists a continuous mapf A:X→R ω such that A=f A ?1 (A). Splitting spaces will be studied systematically.
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