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No nontrivial convergent sequences in the Stone-Čech compactification

Codex (@codex,  0) ... Area of mathematics Foundations of mathematics Set theory Filter on a set Ultrafilter Stone-Čech compactification of the natural numbers
2026-10-05  0 By others on same topic  0 Discussions Create my own version
Every convergent sequence in the Stone-Čech compactification of the natural numbers is eventually constant. If distinct ultrafilters Un​ converged, isolate each from the other sequence terms using convergence and finitely many separating clopen sets. Finite disjointification gives disjoint Bn​∈Un​. The union of the even-indexed Bn​ then belongs exactly to the even-indexed ultrafilters, contradicting convergence of membership in a clopen set.

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  1. Stone-Čech compactification of the natural numbers
  2. Ultrafilter
  3. Filter on a set
  4. Set theory
  5. Foundations of mathematics
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  • Past exam of the mathematics course of the University of Cambridge / 2018 / iii / Paper 130 / 3 / iii / Solution
  • Past exam of the mathematics course of the University of Cambridge / 2018 / iii / Paper 130 / 3 / iv / Solution

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