1^∞, 0^0 and others on the real projective line

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Discussion Overview

The discussion revolves around the mathematical concepts of indeterminate forms such as 1^∞, 0^0, and others, particularly in the context of the real projective line and infinity. Participants explore various interpretations and implications of these forms, including their relationships to limits and arithmetic operations involving infinity.

Discussion Character

  • Exploratory
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant proposes that under certain conditions, expressions like 0*∞, ∞/∞, and 0/0 can be treated as a 'collection' of numbers, referred to as A.
  • Another participant suggests that the real projective line could be represented as a circular graph, allowing arithmetic calculations to be performed using angular measures.
  • There is a discussion about how limits can be interpreted differently, with one participant asserting that substituting infinity into limits can yield meaningful results.
  • One participant expresses confusion over the arithmetic of infinity, stating that ∞/0 and 0/∞ yield results that lead back to A.
  • Another participant challenges the arithmetic operations involving infinity, arguing that such operations are fundamentally flawed.
  • A participant introduces the concept of limit points, suggesting that the set of limit points can provide insights into functions approaching infinity.
  • There is a proposal that A might represent an intermediate range of values between 0 and infinity, raising philosophical questions about the nature of these quantities.
  • Some participants express frustration with the notation and definitions surrounding these concepts, indicating a need for clarity.
  • One participant humorously notes their struggle with writing and note-taking, reflecting a broader theme of the challenges faced in discussing complex mathematical ideas.

Areas of Agreement / Disagreement

Participants express a range of views on the arithmetic of infinity and the interpretations of indeterminate forms. There is no consensus on the validity of treating infinity as a number or on the implications of the proposed definitions and operations involving A.

Contextual Notes

The discussion includes various assumptions about the behavior of infinity and the definitions of indeterminate forms, which remain unresolved. The mathematical steps and implications of these assumptions are not fully clarified.

  • #31
Hurkyl is exactly right.

I said earlier that these things are not defined, because when you define them you get contractions.

Wouldn't you agree that 0≠0 is a contradiction?

This is why we leave these things undefined.
 
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  • #32
Diffy said:
Hurkyl is exactly right.

I said earlier that these things are not defined, because when you define them you get contractions.
The reason they aren't defined is because it's not useful to define them.

It's not useful to define them, because if you did, it wouldn't have many useful properties.

You only get a contradiction if you both define them and assume that the definition has useful properties.
 
  • #33
Hurkyl said:
The reason they aren't defined is because it's not useful to define them.

It's not useful to define them, because if you did, it wouldn't have many useful properties.

You only get a contradiction if you both define them and assume that the definition has useful properties.
While I agree in principle, I've sometimes found it useful to define 0^0 as 1.
 
Last edited:
  • #34
MTannock said:
While I agree in principle, I've sometimes found it useful to define 0^0 as 1.
Hurkyl was referring to ∞/∞ and 0/0.

A lot of calculators agree with you on 0^0, and produce 1 as a result. This doesn't have anything to do with the real projective line or the extended real number line, though.
 
  • #35
Actually, 0^0 is relevant here. It's also a wonderful illustration of some of the relevant problems.

On the one hand, is not useful to give a value to 0^[/color]0. On the other hand, 0^[/color]0 is not only equal to 1, but it's not even a special case.

What changed from one side to the other is that ^[/color] refers to the continuous exponentiation operator or its continuous extensions to things like the extended and projective real lines. ^[/color], however, is being used to some sort of algebraic exponentiation operator; examples have domains including things like the base from any ring and exponent from the natural numbers. The exponentiation operation appearing in a power series is ^[/color].
 

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