Lebl-Basic-Analysis-I · Problem 7.4.8

Metric Spaces

Mathematics · compactness

Problem

(Challenging) Let C([0,1],R)C\bigl([0, 1], \mathbb{R}\bigr) be the metric space of Example 7.1.8. Let 00 denote the zero function. Then show that the closed ball C(0,1)C(0, 1) is not compact (even though it is closed and bounded). Hints: Construct a sequence of distinct continuous functions {fn}n=1∞\{f_n\}_{n=1}^\infty such that d(fn,0)=1d(f_n, 0) = 1 and d(fn,fk)=1d(f_n, f_k) = 1 for all n≠kn \neq k. Show that the set {fn:n∈N}⊂C(0,1)\{f_n : n \in \mathbb{N}\} \subset C(0, 1) is closed but not compact. See chapter 6 for inspiration.

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