Solve Connected Set Closure: Show Not Disconnected

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Discussion Overview

The discussion revolves around the question of whether the closure of a connected set is itself connected. Participants explore various approaches to demonstrate that the closure cannot be disconnected, considering different scenarios and definitions of connectedness.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant expresses uncertainty about how to show that the closure of a connected set is connected, indicating a struggle with the foundational concepts.
  • Another participant suggests a method involving the closure of the set being contained within two disjoint open sets, X and Y, and proposes that if this is the case, then the closure must be contained in either X or Y.
  • A different participant questions whether the problem can be solved if the closure includes one or two additional points, implying that the number of points may affect the connectedness.
  • Another participant introduces a definition of connectedness that states a set is connected if all continuous maps to the set {0,1} are constant, suggesting that this perspective could simplify the problem.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the best approach to demonstrate the connectedness of the closure. Multiple competing views and methods are presented, indicating that the discussion remains unresolved.

Contextual Notes

Some assumptions about the nature of the space and the definition of connectedness may be implicit in the discussion, but these are not explicitly stated. The implications of adding points to the closure are also not fully explored.

Who May Find This Useful

This discussion may be of interest to students and researchers in topology, particularly those exploring concepts of connectedness and closure in mathematical spaces.

metalbec
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I'm struggling with something that I suspect is very basic. How do I should that the closure of a connected set is connected? I think I need to somehow show that it is not disconnected, but that's where I'm stuck.

Thanks
 
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Call your space [tex]M[/tex]. You want to show that if [tex]\mathrm{cl}(M) \subset X\cup Y[/tex], with [tex]X, Y[/tex] disjoint and open then [tex]\mathrm{cl}(M)[/tex] is contained in either [tex]X[/tex] or [tex]Y[/tex].

Can you go from here?
 
Can you solve the problem if the closure has one additional point?
How about two additional points?
 
the following version of connectedness makes all possible problems trivial:

a set is connected iff all continuous maps to the set {0,1} are constant.
 

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