| ultrafilter |
In mathematics, especially in order theory, an ultrafilter is a subset of a partially ordered set (a poset) which is maximal among all proper filters. Formally, this states that any filter that properly contains an ultrafilter has to be equal to the whole poset. An important special case of the concept occurs if the considered poset is a Boolean algebra, like in the case of an ultrafilter on a set (defined as a filter of the corresponding powerset). ...
출처: en.wikipedia.org/wiki/Ultrafilter
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