Topology Problems for Challenging Students

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Discussion Overview

The discussion revolves around the search for challenging topology problems suitable for a course aimed at engaging students more effectively. Participants share various problem ideas that could stimulate students' thinking and understanding of topology concepts, while also addressing the challenges of the current educational system regarding problem-solving expectations.

Discussion Character

  • Exploratory
  • Debate/contested
  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant expresses a desire to challenge students with difficult yet solvable topology problems, emphasizing the need for engaging and intuitive questions.
  • Proposed problems include:
    • \mathbb{R} cannot be written as the disjoint union of closed intervals.
    • Constructing a space that is connected but not path connected.
    • Finding a complete metric space whose metric is bounded but not compact.
    • Exploring the properties of the Cantor set and variations thereof.
    • Showing that the Euler characteristic of a polygon is independent of triangulation.
  • Some participants suggest using textbooks like Munkres or Hatcher for reference.
  • One participant raises a question about the convergence of sequences in the finite complement topology on \mathbb{R} and its implications for non-Hausdorff spaces.
  • Another participant challenges the assertion that \mathbb{R} cannot be written as a disjoint union of closed intervals, suggesting that it can if intervals contain more than one element.
  • Discussion includes a critique of a proposed problem regarding connected sets, with one participant arguing that the suggested set is not connected.
  • Several participants express enthusiasm for the proposed problems and their potential to provoke deeper thought among students.

Areas of Agreement / Disagreement

Participants generally agree on the need for challenging problems but express differing opinions on specific problem formulations and their implications. Some disagreements arise regarding the properties of certain sets and the validity of proposed problems.

Contextual Notes

Some problems may depend on specific definitions or assumptions that are not universally agreed upon. For example, the discussion about the disjoint union of closed intervals and the properties of connected sets highlights varying interpretations and understandings of topology concepts.

Who May Find This Useful

Educators and students interested in topology, particularly those looking for engaging problems to enhance understanding and stimulate discussion in a classroom setting.

  • #31
lavinia said:
no. try putting such a metric on the unit disk.

I'm sorry, I really don't understand.

What would be wrong with my metric on the unit disk? Maybe you misunderstood what I was saying- I define a new metric in terms of the older one. For any metric d, we can construct another one (called d^, say) which is defined as being equal to d except when d evaluates to a number larger than 1, in which case, you set d^ to return the value 1.
 
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  • #32
Jamma said:
I'm sorry, I really don't understand.

What would be wrong with my metric on the unit disk? Maybe you misunderstood what I was saying- I define a new metric in terms of the older one. For any metric d, we can construct another one (called d^, say) which is defined as being equal to d except when d evaluates to a number larger than 1, in which case, you set d^ to return the value 1.

The unit disk under the usual metric and your modification, is compact.
 
  • #33
lavinia said:
The unit disk under the usual metric and your modification, is compact.

Oh, I think I see what you are getting at. I wasn't trying to imply that this procedure makes the space non-compact (the topology will be unaltered). All I'm saying is that for any non-compact complete metric space you can think of, if the metric isn't bounded then you can simply bound it in the way I described.
 

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