How to compute the cohomology of the Klein bottle

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In summary, the conversation discusses using the Mayer-Vietoris sequence to calculate the De Rham cohomology of the Klein bottle. The first step is to find a good open cover, which can be done using two Mobius strips. However, it is important to compute their cohomology correctly and not confuse the Klein bottle with the torus. The conclusion is that the Klein bottle and the torus have the same cohomology.
  • #1
TFT
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Using the Mayer–Vietoris sequence, how can we calculate the
De Rham cohomology of the Kelin bottle?
 
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  • #2
First step would be to find a good open cover. Have you done so yet?
 
  • #3
morphism said:
First step would be to find a good open cover. Have you done so yet?


Yes, I used tow cylinders to cover it. The result I got this way shows that Klein bottle has the same cohomology as the torus. I am not sure whether this is correct.
 
  • #4
I don't think those are cylinders ;)

Once you figure out what they are (and compute their cohomology, which is pretty straightforward), you'll have the answer.
 
  • #5
zhentil said:
I don't think those are cylinders ;)

Once you figure out what they are (and compute their cohomology, which is pretty straightforward), you'll have the answer.

You are right. But still they have the sam cohomology as the cylinder, which is the same as the cohomology of the circle. In this way, I got the result that the Klein bottle and the torus have the same cohomology. I do not know if this is correct, but I think I am doing the right thing.
 
  • #6
Why do they have the same cohomology as the cylinder? That's certainly not true.
 
  • #7
zhentil said:
Why do they have the same cohomology as the cylinder? That's certainly not true.

They are two Mobius strips, right? So they have the same cohomology as the circle.
 
  • #8
That's the open cover I had in mind. Those two mobius strips and their intersection (another mobius strip) have the cohomology of the circle. In fact, it turns out that the Klein bottle does as well.

So either you haven't computed the cohomology of the torus correctly, or you're messing up the MV argument.
 
  • #9
morphism said:
That's the open cover I had in mind. Those two mobius strips and their intersection (another mobius strip) have the cohomology of the circle. In fact, it turns out that the Klein bottle does as well.

So either you haven't computed the cohomology of the torus correctly, or you're messing up the MV argument.

Yeah, I did mess up with MV. I got it now. Thanks guys.
 

1. What is the Klein bottle?

The Klein bottle is a non-orientable surface, meaning it has only one side and cannot be embedded in 3-dimensional space without self-intersection. It is often represented as a 2-dimensional shape with no edges or corners.

2. Why is computing the cohomology of the Klein bottle important?

The cohomology of a topological space is a fundamental tool in algebraic topology, providing information about the shape and structure of the space. Understanding the cohomology of the Klein bottle can also lead to insights about other non-orientable surfaces and more complex spaces.

3. What is the process for computing the cohomology of the Klein bottle?

The cohomology of the Klein bottle can be computed using various methods, such as Mayer-Vietoris sequences, cellular cohomology, or spectral sequences. Each method involves breaking down the Klein bottle into smaller, easier-to-analyze parts and then using algebraic techniques to compute the cohomology.

4. Can the cohomology of the Klein bottle be computed using computer programs?

Yes, there are computer programs that can compute the cohomology of the Klein bottle and other topological spaces. These programs use algorithms and mathematical techniques to efficiently compute the cohomology and can handle more complex spaces than can be done by hand.

5. What are some applications of the cohomology of the Klein bottle?

The cohomology of the Klein bottle has applications in various fields, such as physics, geometry, and topology. It can be used to study symmetries and invariants of non-orientable surfaces, and it has connections to other mathematical concepts such as group theory and differential geometry.

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