Dedekind Cuts & the Real Line: A Countable Set?

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Dedekind cuts can represent real numbers that are not rational, challenging the notion that they only produce a countable set. Each Dedekind cut is defined by a set of rational numbers, but these sets can converge to irrational numbers. For instance, a sequence of rational numbers can be derived from the decimal expansion of a real number, forming a cut that represents that real number. An example is the cut defined by the set of rationals whose squares are less than 2, which cannot be classified as a rational cut. Thus, Dedekind cuts encompass the entirety of the real line, including irrational numbers.
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If every Dedekind cut is at a rational it seems that these cuts would only produce a countable set and would not produce the whole real line. So how should I think about it.
 
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cragar said:
If every Dedekind cut is at a rational it seems that these cuts would only produce a countable set and would not produce the whole real line. So how should I think about it.

The point is that there are Dedekind cuts that are NOT at rationals.
For example, take any real number A and consider its decimal expansion. A sequence of rational numbers An can be defined by taking n terms of the expansion. Let the cut be defined by all rationals less than any term in the sequence. This cut gives the real number A.
 
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Even though all Dedekind cuts consist of only rational numbers, all are not rational cuts.
T = { x \in Q: x^2 < 2 or x < 0 } is a dedekind cut, you can check that all the properties hold, but it can not be a rational cut.
 
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