Can you me proving , uniform convergence implies pointwise convergence

In summary, the conversation is about the definitions of uniform convergence and convergence, and the difference between them. Uniformly convergent means that for any given value of \epsilon, the same \delta can be used for every value of x. In contrast, with just "convergent", \delta may vary depending on \epsilon and the value of x.
  • #1
shehpar
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I don't know, I started from the definition of uniform convergence and it seems pretty obvious to me , can anybody start me at least towards right direction?
 
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  • #2


Yes, that pretty much all it takes.

Definition of "uniformly convergent": [itex]\{f_n(x)\}[/itex] converges to f(x) as n goes to infinity uniformly if and only if, given [itex]\epsilon> 0[/itex], there exist N such that if n > N, then [itex]|f_n(x)- f(x)|< \epsilon[/itex].

Definition of "convergent": [itex]{f_n(x)}[/itex] converges to f(a) for given a as n goes to infinity if and only if given [itex]\epsilon> 0[/itex], there exsit N such that if n> N, then [itex]|f_n(a)- f(a)|< \epsilon[/itex].

Basically, "uniformly convergent" requires that, given [itex]\epsilon[/itex], you be able to use the same [itex]\delta[/itex] for every value of x. Just "convergent" means the value of [itex]\delta[/itex] may depend upon [itex]\epsilon[/itex] and the value of x at which the function is evaluated.
 

1. What is the definition of uniform convergence?

Uniform convergence is a type of convergence of a sequence of functions where the convergence occurs at a constant rate, regardless of the specific point in the domain of the function.

2. How is uniform convergence different from pointwise convergence?

Pointwise convergence refers to the convergence of a sequence of functions to a specific point in the domain, whereas uniform convergence refers to the convergence occurring uniformly across the entire domain.

3. Can you provide an example of a sequence of functions that demonstrates uniform convergence implies pointwise convergence?

A classic example is the sequence of functions f_n(x) = x^n on the interval [0,1]. This sequence converges pointwise to the function f(x) = 0 for x in [0,1), and f(x) = 1 at x = 1. However, this sequence converges uniformly to the function f(x) = 0 for all x in [0,1].

4. What are some applications of uniform convergence?

Uniform convergence is commonly used in analysis, particularly in proving the continuity of a function or the interchangeability of limits and integrals. It also has applications in numerical analysis and the study of differential equations.

5. Are there any conditions for uniform convergence to imply pointwise convergence?

Yes, in order for uniform convergence to imply pointwise convergence, the functions in the sequence must be continuous and the domain must be a compact set. Additionally, the pointwise limit function must also be continuous.

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