Density of Irrational Numbers in [0;1]

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Discussion Overview

The discussion revolves around the density of irrational numbers in the interval [0, 1], specifically examining the set defined by the expression ##\{nx - \lfloor{nx} \rfloor / n \in \mathbb{N}\}## where ##x## is an irrational number. Participants explore the implications of this density and seek to establish formal proofs or references related to the topic.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant suggests that the density of irrational numbers in [0, 1] can be intuitively understood by considering any two numbers in that interval, asserting that there exists an irrational number between them.
  • Another participant emphasizes the formal definition of a dense subset and mentions the need for a rigorous proof that irrational numbers can be found arbitrarily close to any rational number.
  • A third participant clarifies that while irrational numbers are indeed dense in ##\mathbb{R}##, they aim to use this property to demonstrate the density of the specific set ##\{nx - \lfloor nx \rfloor / n \in \mathbb{N}\}## in [0, 1].
  • Links to external resources are provided by participants, referencing a theorem that may relate to the discussion.

Areas of Agreement / Disagreement

Participants express differing views on the approach to proving the density of the specified set. While there is a general agreement on the density of irrational numbers, the application to the specific set remains a point of exploration without consensus on the proof method.

Contextual Notes

The discussion includes references to formal definitions and theorems, but lacks detailed mathematical proofs or explicit assumptions that may be necessary for a complete understanding of the density claims.

Calabi
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Hello, let be ##x \in \mathbb{R} - \mathbb{Q}##, do we have de density of ##\{nx - \lfloor{nx} / n \in \mathbb{N}\}## in ##[0; 1]## please?

I think yes but it's just an intuition : if I take a and b in ##[0; 1]## with a < b, I have an irrationnal between them let call it c but I don't know hat to do with it.

Could you help me please?

Thank you in advance and have a nice afternoon:oldbiggrin:.
 
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In principle you already have said what you need. How is a dense subset formally defined? It might be a bit of work to formally prove that there are always irrational numbers as close to a given rational one as wanted. But given this fact, it's basically the definition of density itself.
E.g.: https://en.wikipedia.org/wiki/Dense_set
 
No that's not what I mean : the irrationnal number are dense in ##\mathbb{R}## so in ##[0; 1]## too (1)
And I wanted to use that to show that
##\{nx - \lfloor nx \rfloor / n \in \mathbb{N}\}## in [0; 1], where x is an irrationnal number, by using (1).
 

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