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| | Dedekind cut - Freepedia (Site not responding. Last check: 2007-11-07) |
 | | In mathematics, a Dedekind cut in a totally ordered set S is a partition of it, (A, B), such that A is closed downwards (meaning that for any element x in S, if a is in A and x ≤ a, then x is in A as well) and B is closed upwards. |
 | | In this way, the set of all Dedekind cuts is itself a linearly ordered set, and, moreover, it does have the least-upper-bound property, i.e., its every nonempty subset that has an upper bound has a least upper bound. |
 | | More generally, in a partially ordered set S, the set of all nonempty downwardly closed subsets (also called order ideals) is a set partially ordered by inclusion, and in the same way we embed S within a larger partially ordered set that, generally unlike the original set S, does have the least-upper-bound property. |
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