Extending the Fundamental Theorem of Arithmetic to the rationals

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Discussion Overview

The discussion revolves around the extension of the Fundamental Theorem of Arithmetic (FTA) to rational numbers. Participants explore whether a similar decomposition of rational numbers into prime factors, allowing for integer exponents, is valid and how it could be formulated. The conversation touches on the implications of such an extension, including uniqueness and the nature of primes in the context of fields versus rings.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that any positive rational number can be expressed as a product of primes with integer exponents, extending the FTA.
  • Others argue that the FTA is fundamentally about primes in the integers and does not apply to rational numbers, as there are no primes in a field like the rationals.
  • One participant suggests that while a rational number can be expressed as a ratio of products of primes, this does not constitute a generalization of the FTA but rather an application of it to both the numerator and denominator.
  • Another viewpoint emphasizes that the uniqueness of such a decomposition for rational numbers is questionable, particularly regarding the distinction between the numerator and denominator.
  • Some participants assert that the theorem's validity relies on the properties of rings, not fields, and that applying it to rational numbers leads to contradictions.
  • There is a contention regarding the definition of primes and irreducible elements in the context of rational numbers, with some asserting that primes cannot be defined in the field of rationals.

Areas of Agreement / Disagreement

Participants generally disagree on the applicability of the FTA to rational numbers. While some believe an extension is possible, others maintain that such an extension is not valid and that the theorem does not hold in the context of rational numbers.

Contextual Notes

Participants highlight limitations regarding the definitions of primes in fields versus rings, and the implications of lifting restrictions on exponents in the context of rational numbers. The discussion remains unresolved regarding the uniqueness and formulation of the proposed extension.

  • #31
Warp said:
I am not sure about the uniqueness, however. Could two different combinations of integers produce the same rational number?
Of course they can \frac{1}{2} and \frac{17}{34} represent the same rational number.

Rationals do not have a unique representation. Every rational number is a member of an equivalence class of combinations of integers.
 
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  • #32
Svein said:
Of course they can \frac{1}{2} and \frac{17}{34} represent the same rational number.

Rationals do not have a unique representation.
But they have a unique reduced form to lowest terms, p/q where GCD(p,q)=1. Then both p and q can be factored uniquely into primes where p and q have no common primes.
 
  • #33
FactChecker said:
But they have a unique reduced form to lowest terms, p/q where GCD(p,q)=1. Then both p and q can be factored uniquely into primes where p and q have no common primes.
The crucial point is the title. The word extension suggests a form of generalization, which it is not. You can't extend from ring to field. No way.
 
  • #34
fresh_42 said:
The crucial point is the title. The word extension suggests a form of generalization, which it is not. You can't extend from ring to field. No way.
There are some formally defined uses of the word "extension", but extending a theorem is not one of those.
In any case, the original question has probably been answered.
 
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  • #35
fresh_42 said:
The crucial point is the title. The word extension suggests a form of generalization, which it is not. You can't extend from ring to field. No way.
It is a generalization in the sense that it is a correct statement which includes unique factorization in the integers as a special case, not in the sense that it deals with prime elements in ##\mathbb{Q}.##
 
  • #36
An application of FTA is something basically different than an extension of FTA.

This is logically relevant as it is algebraically. To throw it all in one pot teaches the wrong motivations. A true statement isn't the same thing as a true classification. All posts above thought to an end would mean: Let's gather all theorems, list them in a book and call it: True. I cannot see how this is doing anyone a favor.
 
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