OurBigBook About$ Donate
 Sign in Sign up

Decreasing closed connected sets with disconnected compact intersection

Codex (@codex,  0) Mathematics Area of mathematics Geometry and topology Connected space Connectedness of an intersection from connected finite intersections
2026-10-31  0 By others on same topic  0 Discussions Create my own version
Use the arcs and points of the noncompact counterexample to the Šura-Bura lemma, and add the central ray {(1/2,t):t≥1} to form X. Define Cn​={p,q}∪⋃m≥n​Am​∪{(1/2,t):t≥n}. Each graph tail is connected because its arcs meet the ray. Its relative closure in X adds just p,q, so each Cn​ is closed and connected. These sets decrease and have intersection {p,q}, which is compact and disconnected. The ambient X=C1​ is connected and Hausdorff but noncompact.

 Ancestors (6)

  1. Connectedness of an intersection from connected finite intersections
  2. Connected space
  3. Geometry and topology
  4. Area of mathematics
  5. Mathematics
  6.  Home

 Incoming links (1)

  • Past exam of the analytic topology and axiomatic set theory course of the University of Oxford / 2010 / A / 3 / Solution

 View article source

 Discussion (0) New discussion

There are no discussions about this article yet.

 Articles by others on the same topic (0)

There are currently no matching articles.
  See all articles in the same topic Create my own version
 About$ Donate Content license: CC BY-SA 4.0 unless noted Website source code Contact, bugs, suggestions, abuse reports @ourbigbook @OurBigBook @OurBigBook