TheoremBase

The Rational Numbers Form an Archimedean Ordered Field Containing the Integers

The rational numbers form an Archimedean ordered field whose strict order is the strict relation of its order; the integers embed into it preserving 0, 1, the operations and the order, two fractions are equal exactly when their cross products agree, and each fraction times its denominator is its numerator.

Statement

In the setting of The Natural Numbers and the Natural Numbers with Zero: Arithmetic, Order, Induction and Recursion, let Z\mathbb{Z}, its operations and order, 0Z0_{\mathbb{Z}}, 1Z1_{\mathbb{Z}} and ι\iota be as in The Integers §integers, The Integers §operations, The Integers §constants and The Integers §embedding, and let Q\mathbb{Q}, [x,m][x,m], its operations and order, 0Q0_{\mathbb{Q}}, 1Q1_{\mathbb{Q}} and jj be as in The Rational Numbers §rationals, The Rational Numbers §operations, The Rational Numbers §constants and The Rational Numbers §embedding. Let x,y∈Zx,y\in\mathbb{Z}, m∈Nm\in\mathbb{N} and u∈Qu\in\mathbb{Q}.

≤\le is a total order on Q\mathbb{Q}, with << as its strict relation, and Q\mathbb{Q}, with ++, ⋅\cdot, 0Q0_{\mathbb{Q}}, 1Q1_{\mathbb{Q}} and ≤\le, is an ordered field; moreover u+(−u)=0Qu+(-u)=0_{\mathbb{Q}}.

jj is injective, j(0Z)=0Qj(0_{\mathbb{Z}})=0_{\mathbb{Q}}, j(1Z)=1Qj(1_{\mathbb{Z}})=1_{\mathbb{Q}}, j(x+y)=j(x)+j(y)j(x+y)=j(x)+j(y), j(xy)=j(x) j(y)j(xy)=j(x)\,j(y), j(−x)=−j(x)j(-x)=-j(x), and x≤yx\le y if and only if j(x)≤j(y)j(x)\le j(y).

[x,m]⋅j(ι(m))=j(x)[x,m]\cdot j(\iota(m))=j(x).

There is k∈Nk\in\mathbb{N} with u<j(ι(k))u<j(\iota(k)).

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