Math 2.0

Real functions The real line Axiom

Completeness axiom

Builds on Real numbersSet bounded aboveSupremum

Statement

Let SS be a nonempty subset of the real numbers that is bounded above. Then SS has a supremum in ℝ\mathbb{R}.

Remarks

In the axiomatic approach, this is the axiom that distinguishes ℝ\mathbb{R} from the other ordered fields. In a construction of ℝ\mathbb{R}, it is a theorem. The ordered field ℚ\mathbb{Q} does not have this property: {q∈ℚ:q2<2}\{q \in \mathbb{Q} : q^2 < 2\} has no supremum in ℚ\mathbb{Q}. The axiom gives the existence of the infimum and the Archimedean property of the reals.

Reading path

To understand this page from the ground up, read these 4 pages in order. The foundations come first.

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  1. Real numbers object
  2. Set bounded above definition
  3. Supremum definition
  4. Completeness axiom statement

Where this leads

280 pages build on this one.

Further reading

  1. Web https://en.wikipedia.org/wiki/Least-upper-bound_property, Statement for real numbers
About this page
Tag0AXWET80YW
URIm2://0AXWET80YW
Aliasesleast-upper-bound-property, supremum-property, dedekind-completeness
Kindstatement, axiom
WritingW0 stub
MSC26A03
StatusThis copy of the site has no build data. Run m2 status 0AXWET80YW.
UsesReal numbers, Set bounded above, Supremum
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