Lipschitz Continuity .... and Continuity in R^n ....

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Discussion Overview

The discussion revolves around the relationship between Lipschitz continuity and continuity in the context of mappings in multidimensional real analysis, specifically as presented in a textbook. Participants are exploring the implications of Lipschitz continuity on the continuity and uniform continuity of functions.

Discussion Character

  • Technical explanation, Conceptual clarification, Mathematical reasoning

Main Points Raised

  • Peter seeks a rigorous proof that Lipschitz continuity implies continuity and uniform continuity of a mapping.
  • One participant suggests a method for demonstrating uniform continuity by choosing a specific delta based on epsilon and a Lipschitz constant.
  • Peter expresses understanding of the proposed method and attempts to verify the reasoning with a mathematical expression.
  • A later reply confirms Peter's understanding of the reasoning presented.

Areas of Agreement / Disagreement

Participants appear to agree on the method proposed for demonstrating uniform continuity, but the discussion does not resolve whether this method constitutes a complete proof of the implications of Lipschitz continuity.

Contextual Notes

The discussion does not provide a complete proof or address all assumptions involved in the definitions of continuity and Lipschitz continuity.

Who May Find This Useful

Readers interested in mathematical analysis, particularly those studying continuity concepts in higher dimensions or exploring properties of functions in real analysis.

Math Amateur
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I am reading "Multidimensional Real Analysis I: Differentiation" by J. J. Duistermaat and J. A. C. Kolk ...

I am focused on Chapter 1: Continuity ... ...

In Definition 1.3.4 D&K define continuity and then go on to define Lipschitz Continuity in Example 1.3.5 ... ... (see below for these definitions ...)I have tried to show that Lipschitz Continuity implies continuity of a mapping f ... but have not succeeded ...

Can someone please demonstrate how to rigorously prove that Lipschitz continuity implies that f is continuous ... (***edit*** ... better still would be to show that Lipschitz continuity implies that f is uniformly continuous ...)Help will be appreciated ...

Peter========================================================================================***Note***

D&K's definitions of continuity and Lipschitz continuity read as follows:https://www.physicsforums.com/attachments/7749Peter
 
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Hi, Peter.

For a given epsilon, choose $\delta=\epsilon/k$. Note that the choice of $\delta$ works for all $x$, which implies uniform continuity.
 
GJA said:
Hi, Peter.

For a given epsilon, choose $\delta=\epsilon/k$. Note that the choice of $\delta$ works for all $x$, which implies uniform continuity.

Thanks GJA ... ...

I think I can see this ... since then we have ...

$$\mid \mid x - x' \mid \mid \Longrightarrow \mid \mid f(x) - f(x') \mid \mid\le k \mid \mid x - x' \mid \mid = k \delta = \epsilon
$$Is that correct?

Peter
 
You got it!
 

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