Why is this homology group is zero?

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In summary, the homology group H1(K) of a triangulation of the 2-sphere is equal to zero because homology groups are abelian and the identity element is written as "zero". This is also the case when the group consists of only a single equivalence class, which is the case for the sphere being simply connected.
  • #1
kakarotyjn
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For example,K is a triangulation of [tex] S^2 [/tex];[tex]H_1 (K ) = Z_1 (K )/B_1 (K )[/tex].And [tex] Z_1 (K ) = B_1 (K ) [/tex].Then I think [tex] H_1(K)=[z][/tex],z is any element of [tex]Z_1(K),[z][/tex] is the equivalent class of z .But why is it zero?Thank you!
 
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kakarotyjn said:
For example,K is a triangulation of [tex] S^2 [/tex];[tex]H_1 (K ) = Z_1 (K )/B_1 (K )[/tex].And [tex] Z_1 (K ) = B_1 (K ) [/tex].Then I think [tex] H_1(K)=[z][/tex],z is any element of [tex]Z_1(K),[z][/tex] is the equivalent class of z .But why is it zero?Thank you!

Your question is a little vague because you are not describing the triangulation of the 2 sphere that you are using and you are not describing the cycle,z.

Be assured that the first homology is zero because the sphere is simply connected.
 
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  • #3
Maybe the question is why we say "zero" for the group consisting of a single equivalence class? In that case, the answer is because homology groups are abelian, so the identity is written as zero, and the group consisting of only the identity is also called "zero".
 
  • #4
Tinyboss said:
Maybe the question is why we say "zero" for the group consisting of a single equivalence class? In that case, the answer is because homology groups are abelian, so the identity is written as zero, and the group consisting of only the identity is also called "zero".

yes. zero is the convention for the identity in abelian groups.
 
  • #5
K would be the same as k K=kMaybe the question is why we say "zero" for the group consisting of a single equivalence class? In that case, the answer is because homology groups are abelian, so the identity is written as zero, and the group consisting of only the identity is also called "zero"
Re: Why is this homology group is zero?
Originally Posted by Tinyboss View Post

Maybe the question is why we say "zero" for the group consisting of a single equivalence class? In that case, the answer is because homology groups are abelian, so the identity is written as zero, and the group consisting of only the identity is also called "zero".

yes. zero is the convention for the identity in abelian groups. Your question is a little vague because you are not describing the triangulation of the 2 sphere that you are using and you are not describing the cycle,z.

Be assured that the first homology is zero because the sphere is simply connected.
and that my friendf is the... answer
 
  • #6
Oh,thank you all! Now I'm clear about it,it is truly consisting one equivalent class.
 

Related to Why is this homology group is zero?

1. Why is this homology group is zero?

The homology group being zero means that there are no cycles in the given space, which ultimately implies that there are no holes or voids in the structure. This could be due to the simplicity of the space or the specific geometric properties it possesses.

2. What does a zero homology group imply?

A zero homology group implies that the given space is simply connected, meaning that any loop in the space can be continuously shrunk to a single point without leaving the space. This is also known as the fundamental group being trivial.

3. Can a space have multiple zero homology groups?

Yes, it is possible for a space to have multiple zero homology groups. This could occur if the space has multiple disconnected components, each with their own trivial fundamental group. In this case, the homology groups would be zero for each component of the space.

4. How does the dimension of a space relate to its homology groups?

The dimension of a space plays a crucial role in determining the homology groups. In general, the homology groups will have a maximum dimension equal to the dimension of the space itself. For example, a 2-dimensional space can have homology groups up to dimension 2, but not higher.

5. What are some real-world applications of studying zero homology groups?

Studying zero homology groups can provide valuable insights in various fields, such as topology, geometry, and computer science. It can help in understanding the connectivity and structural properties of a space, as well as in designing algorithms for data analysis and processing. In physics, zero homology groups can also play a role in understanding the topology of spacetime and the behavior of physical systems.

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