Proving Continuity of g: C0([0, 1]) x [0, 1]-->R

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Homework Help Overview

The problem involves proving the continuity of a function g defined from the set of continuous functions on the interval [0, 1] with the supremum topology to the real numbers. The function g takes a continuous function and a point in the interval and returns the value of the function at that point.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss various methods to prove continuity, including the potential use of the Urysohn lemma and examining pre-images. There is also a suggestion to show continuity directly by manipulating the expression |f(a) - g(b)| and considering uniform continuity due to the compactness of the interval.

Discussion Status

The discussion is active, with participants exploring different approaches and clarifying concepts related to continuity. Some guidance has been offered regarding direct methods and the implications of uniform continuity, but no consensus has been reached on a specific approach.

Contextual Notes

Participants are working within the constraints of the supremum topology and the properties of continuous functions on a compact interval, which are relevant to the proof of continuity being discussed.

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Homework Statement


Let C0([0, 1]) be the set of continuous functions on the interval [0, 1] with the supremum topology. Prove that the map given by g: C0([0, 1]) x [0, 1]-->R given by g(f, a) = f(a) is continuous.


The Attempt at a Solution


I was originally thinking that maybe I could use the Urysohn lemma to show continuity, but I could not figure out how to make that work in a proof. The simpler method of looking at pre-images of g has also not yielded any insight so far. Any help would be appreciated.
 
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Can't you just show it directly? Given f and a you want to make |f(a) - g(b)| small if g is close to f in the sup norm and a is close to b. Try adding and subtracting f(b).
 
Ok, you want to show |f1(a1)-f(a)| is close to 0 where f1 is close to f in the supremum topology and a1 is close to a. Did you use that f is uniformly continuous on [0,1] since [0,1] is compact?
 
Yeah, you're right. I was over thinking the problem. Thanks for the help.
 

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