TheoremBase

Multiplication of Dedekind Cuts: Associativity, Commutativity, Unit, Distributivity, Reciprocals and Nonnegative Products

Multiplication of Dedekind cuts is associative, commutative and distributive over addition, has the cut of 1 as unit, gives every nonzero cut a reciprocal, keeps products of nonnegative cuts nonnegative, and multiplies rational cuts like the rationals.

Statement

In the setting of The Integers and the Rational Numbers, with the Natural Numbers and the Integers Identified with Subsets of the Rationals, let CC, ≤C\le_{C} and u∗u^{*} for u∈Qu\in\mathbb{Q} be as in Construction of the Dedekind Cuts: They Form a Set Totally Ordered by Inclusion, Closed under Sums, Negatives and Products of Nonnegative Cuts, and let ++, ⋅\cdot, 0R0_{\mathbb{R}} and 1R1_{\mathbb{R}} be as in The Real Numbers §operations and The Real Numbers §constants (so that R=C\mathbb{R}=C, by The Real Numbers §reals). Let x,y,z∈Cx,y,z\in C and u,v∈Qu,v\in\mathbb{Q}.

(x⋅y)⋅z=x⋅(y⋅z)(x\cdot y)\cdot z=x\cdot(y\cdot z), x⋅y=y⋅xx\cdot y=y\cdot x, x⋅1R=xx\cdot1_{\mathbb{R}}=x and x⋅(y+z)=x⋅y+x⋅zx\cdot(y+z)=x\cdot y+x\cdot z.

0R≠1R0_{\mathbb{R}}\neq1_{\mathbb{R}}.

If x≠0Rx\neq0_{\mathbb{R}}, there is w∈Cw\in C with x⋅w=1Rx\cdot w=1_{\mathbb{R}}.

If 0R≤Cx0_{\mathbb{R}}\le_{C}x and 0R≤Cy0_{\mathbb{R}}\le_{C}y, then 0R≤Cx⋅y0_{\mathbb{R}}\le_{C}x\cdot y.

(u⋅v)∗=u∗⋅v∗(u\cdot v)^{*}=u^{*}\cdot v^{*}.

Proofs

Log in to submit a proof.

Loading...

Citations

Loading…

Dependencies

Loading…

Related

0 relations

Curated associations between results. These are editable and subjective — they do not replace the dependency graph, which is derived from the references in the text.

No relations recorded yet.

Comments

Log in to comment.

Loading…