Finite cartesian product of connected space is connected

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Discussion Overview

The discussion revolves around the theorem stating that the finite Cartesian product of connected spaces is connected. Participants are exploring the concepts of base points, homeomorphisms, and the proof structure related to this theorem, seeking clarification on specific steps and ideas presented in a textbook by Munkres.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant expresses confusion regarding the theorem and asks for clarification on the concept of a base point and its relation to homeomorphism.
  • Another participant suggests linking to a proof and identifying specific difficulties encountered in understanding it.
  • A mathematical statement is presented regarding the union of non-empty disjoint opens in the context of Cartesian products.
  • Participants discuss the relevance of the base point in Munkres' proof, with one stating it is an arbitrary point that serves as a common point in the theorem.
  • There is a request for clarification on how the common point (a,b) is related to the chosen sets T's, indicating a lack of understanding of the selection process for these sets.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the understanding of the proof or the role of the base point, indicating ongoing confusion and multiple viewpoints regarding these concepts.

Contextual Notes

Participants express uncertainty about specific steps in the proof and the implications of the base point, suggesting that foundational concepts may be missing or not fully understood.

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"finite cartesian product of connected space is connected"

hi am not able understand the theorem that.. "finite cartesian product of connected space is connected".. what is a base point? how it is related to homeomorphism? can anyone explian?
 
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It would help if you could link to a proof that you have tried to study, and point out the step you're having difficulties with. (See if you can find the relevant page at Google Books).
 


If

A\times B=U\cup V

with U,V nonempty disjunct opens, then

A=\pi_A(U\cup V)=\pi_A(U)\cup \pi_A(V)

or

B=\pi_B(U\cup V)=\pi_B(U)\cup \pi_B(V)

is the union of two non-empty disjoint opens. (Here \pi_C is the projection onto C.)
 


Fredrik said:
It would help if you could link to a proof that you have tried to study, and point out the step you're having difficulties with. (See if you can find the relevant page at Google Books).


no am not able get any idea in that proof..in james.r.munkres book it is given that..
i can only get the idea that it is proved by the use of homeomorphism.. I am not getting the idea how it is related to that figure given.. and the base point.. i think there is something very basic which i need to get..
 


no am not able get any idea in that proof..in james.r.munkres book it is given that..
i can only get the idea that it is proved by the use of homeomorphism.. I am not getting the idea how it is related to that figure given.. and the base point.. i think there is something very basic which i need to get..
 


What Munkres wants to do is apply theorem 23.3. The point in common in that theorem is what he calls the "base point". The base point is just an arbitrary point that will become the "point in common". If you don't get it, then just forget that he mentioned base point. It's not at all important for the proof...
 


ok so base point is just an arbitrary point.. it says that the union of all the Ts are connected because it has (a,b) as the common point.. how come (a,b) common to all the Ts.? can u explain it.?am not getting it..
 


Because you choose the T's exactly so that (a,b) lies on them. How did you choose the T's?
 

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