Is C([0,1]) a Topological Vector Space?

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Discussion Overview

The discussion revolves around whether the space C([0,1]), consisting of all complex-valued continuous functions on the interval [0,1], qualifies as a topological vector space. Participants explore the necessary conditions for this classification, including continuity of vector addition and scalar multiplication within the context of a defined metric.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant defines a metric d for C([0,1]) and asserts that it is an invariant metric space, suggesting that this is a starting point for proving it is a topological vector space.
  • Another participant challenges the first to provide a proof rather than simply stating the problem.
  • A different participant notes that if C([0,1]) is already established as a metric space and a vector space, it suffices to show the continuity of the operations F(f, g) = f + g and F(a, f) = af.
  • Some participants express uncertainty about how to demonstrate the continuity of the operation F(a, f) = af, requesting hints or guidance.
  • One participant suggests using the definitions of continuity to approach the problem, while another recommends employing the epsilon-delta formulation of continuity, indicating a potential method for proving the required continuity.

Areas of Agreement / Disagreement

There is no consensus on how to prove the continuity of scalar multiplication in C([0,1]). Participants express differing levels of understanding and approaches to the problem, indicating that the discussion remains unresolved.

Contextual Notes

Participants have not fully explored the implications of the metric space properties or the definitions of continuity in this context, leaving some assumptions and steps in the proof process unaddressed.

dori1123
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Let C([0,1]) be the collection of all complex-valued continuous functions on [0,1].
Define d(f,g)=\int\limits_0^{1}\frac{|f(x)-g(x)|}{1+|f(x)-g(x)|}dx for all f,g \in C([0,1])
C([0,1]) is an invariant metric space.
Prove that C([0,1]) is a topological vector space
 
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No thanks. Why don't you prove it for us?
 
If you have already proved that C([0, 1]) is a metrix space, and it is clearly a vector space, all you need to prove is that the functions F(f, g)= f+ g and F(a, f)= af are continuous.
 
I don't know how to show F(a,f)=af is continuous, can I get some hints please.
 
dori1123 said:
I don't know how to show F(a,f)=af is continuous, can I get some hints please.
Have you tried using the definitions? Or tried anything at all?

(P.S. you should always try to use the definitions when you're stuck on any problem)
 
F is continuous if for every open subset U of Y, F^{-1}(U) is open in X.
So I let U be an open subset in Y, and let (a,f) be in F^{-1}(U). Then F(a,f) is in U. then I am stuck...
 
Since you've got a metric space, it might be easier to use the epsilon-delta formulation of continuity to show it.
 

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