Proof of Jordan-Brouwer Separation Theorem Using Homotopy Theory?

In summary, the conversation discusses the possibility of using the van Kampen Theorem for higher homotopy groupoids to prove the Jordan-Brouwer Separation Theorem, but it is concluded that this approach is not possible. The article mentioned in the conversation only uses the van Kampen Theorem for the fundamental groupoid of a space, which is not enough to prove the Jordan-Brouwer Separation Theorem. Instead, the proof of the Jordan-Brouwer Separation Theorem requires the use of more advanced tools such as homology and cohomology.
  • #1
jgens
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The other day I found an article which proved the Jordan Curve Theorem using the van Kampen Theorem for the fundamental groupoid of a space. I was wondering if this technique could be extended to prove the more general Jordan-Brouwer Separation Theorem, using higher homotopy groupoids, the "van Kampen Theorem" for higher homotopy groupoids, or something else along these lines. I think it would be interesting if such an approach were possible.

Here's the article I mentioned: http://www.maths.ed.ac.uk/~aar/jordan/pb-jord.pdf
 
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  • #2
Unfortunately, it does not seem that the approach in this article can be extended to prove the Jordan-Brouwer Separation Theorem. The van Kampen Theorem only applies to the fundamental groupoid of a space, which is not powerful enough to capture the essential features of the Jordan-Brouwer Separation Theorem. The Jordan-Brouwer Separation Theorem requires a more sophisticated tool than the van Kampen Theorem, namely the theory of homology and cohomology.
 

1. What is the Jordan-Brouwer Separation Theorem?

The Jordan-Brouwer Separation Theorem is a topological result that states that any closed and bounded subset of n-dimensional Euclidean space divides it into two disjoint connected components. This means that any loop in the space must either be contained entirely within one component or must intersect both components.

2. How is homotopy theory used to prove the Jordan-Brouwer Separation Theorem?

Homotopy theory is a branch of algebraic topology that studies continuous deformations of spaces. In the proof of the Jordan-Brouwer Separation Theorem, homotopy theory is used to show that there exists a continuous map from the n-dimensional space to the unit sphere, which is known as a retraction of the space. This retraction is used to construct the two components of the space that satisfy the conditions of the theorem.

3. What are the key concepts in the proof of the Jordan-Brouwer Separation Theorem?

The key concepts in the proof of the Jordan-Brouwer Separation Theorem are homotopy, retraction, and connectedness. Homotopy is used to show the continuous deformation of the space, while retraction is used to construct the components of the space. Connectedness is necessary to ensure that the components are disjoint and connected.

4. Are there any limitations to the Jordan-Brouwer Separation Theorem?

Yes, the Jordan-Brouwer Separation Theorem is only applicable to closed and bounded subsets of n-dimensional Euclidean space. It does not hold for more general topological spaces, such as non-Euclidean spaces or infinite-dimensional spaces. Additionally, the theorem only guarantees the existence of two disjoint components and does not provide any information about their shape or size.

5. How is the Jordan-Brouwer Separation Theorem relevant in mathematics and other fields?

The Jordan-Brouwer Separation Theorem has applications in various fields, including topology, geometry, physics, and computer science. In topology, it is used to study the properties of surfaces and higher-dimensional spaces. In geometry, it is used to understand the shapes of objects and their boundaries. In physics, it has been used to prove the existence of stable particles in quantum field theory. In computer science, it is used in algorithms for shape recognition and collision detection.

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