Dedekind cut

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A subdivision of the set of real (or only of the rational) numbers (of) into two non-empty sets and whose union is , such that for every and . A Dedekind cut is denoted by the symbol . The set is called the lower class, while the set is called the upper class of . Dedekind cuts of the set of rational numbers are used in the construction of the theory of real numbers (cf. Real number). The concept of continuity of the real axis can be formulated in terms of Dedekind cuts of real numbers.


For the construction of from using cuts see [a1].


[a1] W. Rudin, "Principles of mathematical analysis" , McGraw-Hill (1953)
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Dedekind cut. Encyclopedia of Mathematics. URL:
This article was adapted from an original article by L.D. Kudryavtsev (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article