Proving Non-Isomorphism: Subgroup and Dihedral Group of Equal Order

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In summary, "prove not isomorphic" refers to demonstrating that two graphs are not isomorphic, meaning that they cannot be rearranged or redrawn to look exactly the same. This can be done by showing that the graphs have different properties or characteristics, such as different numbers of vertices, edges, or cycles. Even if two graphs have the same number of vertices and edges, they may still not be isomorphic because isomorphism also takes into account the overall structure and connectivity of the graphs. Proving not isomorphic is important in graph theory as it helps to distinguish between different types of graphs and can have practical applications. While there are some common properties that can be quickly checked, there is no universal shortcut or trick for proving not is
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physix123
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how would you go about showing that a subgroup and dihedral group- of the same order- are not isomorphic?
 
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  • #2
Counterexample.
 
  • #3
Sub group of WHAT? The "dihedral group" of a specified order is the reflection and rotations group of a polygon but you would have to say what subgroup, of what group you want to show is not isomorphic to that. I imagine there must exist SOME subgroup, of SOME group, that is isomorphic to a dihedral group. Did you mean to say, "show that a subgroup of a dihedral group cannot be isomorphic to another dihedral group"?
 

1. What is meant by "prove not isomorphic"?

"Prove not isomorphic" is a statement that is used in graph theory to indicate that two given graphs are not isomorphic, meaning that they cannot be rearranged or redrawn to look exactly the same. It is a way of proving that two graphs are structurally different.

2. How do you prove that two graphs are not isomorphic?

In order to prove that two graphs are not isomorphic, you need to demonstrate that they have different properties or characteristics, such as different numbers of vertices, edges, or cycles. You can also look at the degree sequence, connectivity, or other structural properties to show that the graphs are not isomorphic.

3. Can two graphs have the same number of vertices and edges, but still not be isomorphic?

Yes, it is possible for two graphs to have the same number of vertices and edges, but not be isomorphic. This is because isomorphism is not just about the number of vertices and edges, but also about the overall structure and connectivity of the graphs.

4. What is the importance of proving not isomorphic?

Proving not isomorphic is important in graph theory because it helps to identify and distinguish between different types of graphs. It also allows us to better understand the properties and relationships between graphs, which can have applications in fields such as computer science and chemistry.

5. Are there any shortcuts or tricks for proving not isomorphic?

There are some common properties that can be quickly checked to determine if two graphs are not isomorphic, such as the number of vertices, edges, and degree sequence. However, there is no universal shortcut or trick for proving not isomorphic, as it ultimately depends on the specific characteristics and properties of the graphs in question.

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