Curiosity on this infinite product

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Discussion Overview

The discussion revolves around the concept of infinite products, specifically the product of the number 2 repeated infinitely. Participants explore the implications of treating this product as a limit and the resulting contradictions that arise from different assumptions about convergence and limits.

Discussion Character

  • Exploratory
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant, Ssnow, presents the infinite product ##p_{n} = 2^n## and notes that it diverges to infinity as ##n## approaches infinity, questioning the validity of setting the product equal to a variable ##x## and deriving ##x=0##.
  • Another participant suggests that if one considers the case where ##x=\infty##, ruling it out could bias the result, indicating a potential flaw in the reasoning.
  • A later reply emphasizes that assuming a limit exists leads to contradictions, using the example of the series ##1+1+1+\ldots## to illustrate that if a limit ##L## exists, it leads to ##1=0##.
  • Another participant, Office_Shredder, points out that the assumption of a limit existing is critical to the argument and that without it, the conclusions drawn may not hold.

Areas of Agreement / Disagreement

Participants express differing views on the validity of assuming a limit exists for the infinite product. While some acknowledge the contradictions that arise from such assumptions, there is no consensus on the implications of these contradictions or the nature of the infinite product itself.

Contextual Notes

The discussion highlights the complexities and potential pitfalls in dealing with infinite products and limits, particularly regarding the assumptions made about convergence and the implications of those assumptions.

Ssnow
Science Advisor
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TL;DR
Curiosity question on the infinite product ##2\cdot 2\cdot 2\cdots ##
Let us consider the infinite products ## p_{n}\,=\, 2\cdot 2\cdot 2 \cdot 2 \cdots 2 \,=\, 2^n## with ##n=1,\ldots ## . Clearly ##p_{n}\rightarrow +\infty## as ##n\rightarrow +\infty##. But if I put the infinity case ## 2\cdot 2\cdot 2 \cdot 2 \cdots \,=\, x## I have ##2\cdot x =x ## so ##x=0##. It is obvious I cannot put ##x=2\cdot 2\cdot 2 \cdot 2 \cdots ## and to try to seach the limit because the product diverges but has this "strange" algebraically formal result a conceptual reason to be (for example it is linked to the way to do the products ?) or it is only wrong and stop here ?
Thank you,
Ssnow
 
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Ssnow said:
Summary:: Curiosity question on the infinite product ##2\cdot 2\cdot 2\cdots ##

Let us consider the infinite products ## p_{n}\,=\, 2\cdot 2\cdot 2 \cdot 2 \cdots 2 \,=\, 2^n## with ##n=1,\ldots ## . Clearly ##p_{n}\rightarrow +\infty## as ##n\rightarrow +\infty##. But if I put the infinity case ## 2\cdot 2\cdot 2 \cdot 2 \cdots \,=\, x## I have ##2\cdot x =x ## so ##x=0##.
Or ##x=\infty##. If you rule out ##\infty## here, then you are biasing the result.
 
@FactChecker thanks, sure ##x=0 \vee x=\infty##. I ask for the absurd solution ##x=0## ...
Ssnow
 
This is a pretty classic thing where you can create fake math. The real issue is that you started off by assuming a limit exists. If there is a limit and it is L (L is a real number), then 2L=L so L=0. But this assumes the limit exists to begin with, which obviously it does not.

You can get more obvious contradictions. 1+1+1+..., If it has a limit of L then 1+L= L so 1=0.
 
@Office_Shredder I think ##1+L=L## imply that ##0L=-1## that is impossible!
In any case from something of false you can deduce everything ... :biggrin:
Thank you!
Ssnow
 

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