Understanding Uniform Convergence: The Role of N and A

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SUMMARY

The discussion centers on the theorem regarding uniform convergence of a sequence of measurable functions converging to a real-valued function f on a measurable set E of finite measure. The key conclusion is that for uniform convergence, the choice of N must not depend on x, contrasting with pointwise convergence where N can vary with x. The participants clarify that the conditions involving ε and δ are crucial for establishing uniform convergence, and the set A must be defined properly to maintain the theorem's integrity.

PREREQUISITES
  • Understanding of measurable functions and sets
  • Familiarity with the concepts of uniform and pointwise convergence
  • Knowledge of ε-δ definitions in analysis
  • Basic measure theory, particularly finite measure sets
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  • Study the definitions and properties of uniform convergence in detail
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  • Investigate the role of measurable sets in convergence theorems
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Mathematics students, particularly those studying real analysis and measure theory, as well as educators looking to clarify the distinctions between uniform and pointwise convergence.

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Homework Statement



I would just like to be pointed in the right direction. I have this theorem:

Let E be a measurable set of finite measure, and <fn> a sequence of measurable functions that converge to a real-valued function f a.e. on E. Then given ε>0 and [itex]\delta[/itex]>0, there is a set A[itex]\subset[/itex]E with mA<[itex]\delta[/itex], and an N such that for all x[itex]\notin[/itex]A and all n≥N,
lfn(x)-f(x)l<ε

To me it appears to be concluding:
Given ε>0 and [itex]\delta[/itex]>0, there is a set A[itex]\subset[/itex]E with mA<[itex]\delta[/itex], and an N such that for all x[itex]\notin[/itex]A and all n≥N,
<fn> converges uniformly to a real-valued function f on E~A.



I know that this isn't case but I don't see why. So my question is what would the conclusion of this theorem need to say, in terms of ε and [itex]\delta[/itex], so that <fn> converges uniformly to a real-valued function f on E~A?


Thank you for your time.
 
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The difference between definitions of uniform and pointwise convergence is really small. What you have there is really uniform convergence. Although I don't see why you need delta and A..
Anyway, the difference is that in uniform convergence N does not depend on x. Swapping the conditions "there exists N" and "for all x" would produce the definition of pointwise convergence.
 

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