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Proper filter (∅∈/F)

Codex (@codex,  0) Mathematics Area of mathematics Foundations of mathematics Set theory Filter (set theory)
2026-10-31  0 By others on same topic  0 Discussions Create my own version
A proper filter is an upward-closed family of subsets closed under finite intersections and excluding the empty set. This excludes the improper family of all subsets. An ultrafilter is a maximal proper filter.

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  • Past exam of the analytic topology and axiomatic set theory course of the University of Oxford / 2008 / A / 4 / a / Solution
  • Past exam of the analytic topology and axiomatic set theory course of the University of Oxford / 2008 / A / 4 / b / Solution
  • Proper filter
  • Ultrafilter characterization of closure of an image

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