Convergence of Sequence ##(p_n)## to ##p##

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    Convergence Sequence
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Discussion Overview

The discussion revolves around the convergence of a sequence ##(p_n)## to a limit point ##p## within a set ##E##. Participants explore the construction of such a sequence, its validity, and the implications of the definitions involved, particularly in the context of metric spaces and real numbers.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant proposes defining the sequence ##(p_n)## as ##\left\{\frac{d(p,q)}{n}\right\}_{n=1}^\infty##, assuming ##p## is a limit point of ##E##.
  • Another participant questions whether ##E## is a subset of ##\mathbb{R}## and provides a counterexample with ##E = \{1\}##.
  • Some participants express that the definition of limit point may be incorrect and seek clarification on the theorem regarding the construction of sequences converging to limit points.
  • A participant mentions that while the approach may be correct, the proof lacks rigor in selecting elements for the subsequence.
  • Concerns are raised about the sequence being a collection of numbers that may not correspond to points in the space, particularly in higher dimensions like ##\mathbb{R}^n##.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correctness of the proposed sequence construction or the definitions involved. Multiple competing views and uncertainties remain regarding the definitions of limit points and the applicability of the proposed sequence in different contexts.

Contextual Notes

There are limitations regarding the assumptions about the set ##E##, the definitions of limit points, and the rigor required in the proof of convergence. The discussion highlights the need for clarity in the context of metric spaces versus general spaces.

Bachelier
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If ##p## is a limit point of ##E## then ##\exists \ (p_n) \ s.t. (p_n) \rightarrow p##

For the sequence construction, can I just define ##(p_n)## as such:

##For \ q \in E, \ \ define \ (p_n) := \left\{\Large{\frac{d(p,q)}{n}} \right\}_{n=1}^\infty##​
 
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Are you assuming E is subset of R?

Try E = {1}.

Edit: I also think your definition of limit point is wrong.
 
pwsnafu said:
Are you assuming E is subset of R?

Try E = {1}.

Edit: I also think your definition of limit point is wrong.

Thanks. I am not looking for the def. of ##l.p.##, rather the theorem that states we can alway construct a seq. converging to any limit point.

Rudin uses a different proof, but I just thought about this one and wanted to see if it is correct.
 
Bachelier said:
Thanks. I am not looking for the def. of ##l.p.##, rather the theorem that states we can alway construct a seq. converging to any limit point.

Rudin uses a different proof, but I just thought about this one and wanted to see if it is correct.

I assume you're working in ##\mathbb{R}^n##? This is true in metric spaces. It's not true in general. Your approach is correct, though your proof is not correct as written. You need to be more rigorous about how you're selecting elements for your subsequence.
 
Notice your sequence is a collection of numbers, which are not necessarily points in your space (i.e., outside of the reals, that I can think of ). For example, in R^n, for n>1, the sequence of numbers d(p,q)/n is not a collection of points in your space.
 
Last edited:

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