Trying to understand terms in a problem

  • Context: Undergrad 
  • Thread starter Thread starter Mr Davis 97
  • Start date Start date
  • Tags Tags
    Terms
Click For Summary
SUMMARY

The discussion centers on proving that two translates of a convex disc, denoted as ##C_1## and ##C_2##, are non-crossing, meaning that both ##C_1 - C_2## and ##C_2 - C_1## cannot be non-connected. The terms "non-crossing" and "non-connected" are rooted in topology, with connectedness defined as a topological space where the only clopen sets are the empty set and the space itself. Participants express the challenge of the problem, indicating that it requires a solid understanding of topology to approach effectively.

PREREQUISITES
  • Basic understanding of topology, specifically the concepts of connectedness and clopen sets.
  • Familiarity with convex sets and their properties in Euclidean space.
  • Knowledge of the definitions and characteristics of convex discs.
  • Ability to interpret mathematical notation and proofs involving set operations.
NEXT STEPS
  • Study the definition and properties of connectedness in topology.
  • Explore the concept of convex sets and their implications in geometric contexts.
  • Learn about clopen sets and their role in topological spaces.
  • Review examples of non-crossing sets in geometric topology.
USEFUL FOR

Mathematics students, particularly those studying topology, geometry, or related fields, will benefit from this discussion as it addresses foundational concepts necessary for understanding complex proofs involving convex sets.

Mr Davis 97
Messages
1,461
Reaction score
44
Here is the problem: Let ##C## be a convex disc in the plane, and ##C_1## and ##C_2## be two translates of ##C##. Prove that ##C_1## and ##C_2## are non-crossing, that is, it isn't possible that both ##C_1 - C_2## and ##C_2 - C_1## are non-connected.

Here is my question: What exactly do the terms "non-crossing" and "non-connected" mean? Are these terms coming from topology?
 
Physics news on Phys.org
Crossing is defined in your problem.

Connectedness is indeed a term from topology. A topological space ##(X, \mathcal{T})## is connected if the only clopen (= both closed and open) sets are ##\emptyset## and ##X##. Or equivalently, ##X## is not a disjoint union of two (non-trivial) open sets.
 
So as someone who has a limited understanding of topology, what would be a hint or a first step for this?
 
Mr Davis 97 said:
So as someone who has a limited understanding of topology, what would be a hint or a first step for this?

How does your book define disk?
 
A convex disc is any compact, convex set with non-empty interior
 
Math_QED said:
How does your book define disk?
Any hints? I feel for someones who knows topology this would be an easy problem
 
Mr Davis 97 said:
Any hints? I feel for someones who knows topology this would be an easy problem

It isn't an easy problem. I can't find a quick proof for your statement. Maybe ask to the person who assigned you this problem. Good luck.
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 13 ·
Replies
13
Views
2K
Replies
12
Views
4K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
2
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 17 ·
Replies
17
Views
4K