Math 2.0

definition

Archimedean ordered field

Definition

An ordered field FF is Archimedean when, for all xx and yy in FF with y>0y > 0, there is a natural number nn with ny>xn y > x. Here nyn y means y+y+⋯+yy + y + \dots + y, with nn terms.

Remarks

With y=1y = 1, the definition gives the Archimedean property: for each xx, some natural number exceeds xx. Conversely, this property implies the definition. An equivalent condition: for each ε>0\varepsilon > 0 in FF, there is a natural number n≥1n \ge 1 with 1/n<ε1/n < \varepsilon. The field of rational functions R(t)\mathbb{R}(t), with the order in which tt is larger than every real number, is not Archimedean.

Explanations

L1 human

You can reach any distance with enough small steps of a fixed size. In an Archimedean field there is no number so large that no multiple of a given positive number can pass it.

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Sources

  1. Web https://en.wikipedia.org/wiki/Archimedean_property, Definition for linearly ordered groups
  2. Web https://en.wikipedia.org/wiki/Archimedean_property, Ordered fields