Determine if G and H are isomorphic

  • Thread starter hyderman
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In summary, the conversation is about determining if two graphs, G and H, are isomorphic and the steps to do so. The first step is to understand the concept of isomorphic, which means that there is a one-to-one correspondence between the vertices of the two graphs and the edges are also the same between corresponding vertices. To determine if G and H are isomorphic, one needs to work out the degree of each vertex in both graphs and try to identify the same degrees in both graphs. The conversation also includes a discussion on the notation used for the graphs and the need for more precise definitions. The final conclusion is that G and H are not isomorphic, as there is no one-to-one correspondence between their vertices and edges.
  • #1
hyderman
28
0
please help by explainig in steps thanks much


Determine if G and H are isomorphic. Justify your answer



http://img252.imageshack.us/img252/9076/25461570nc6.jpg
 
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  • #2
You must show some work before we can help. One possible approach is to work out the degree of the vertices in each graph and try to identify those in G with those in H.
 
  • #3
cristo said:
You must show some work before we can help. One possible approach is to work out the degree of the vertices in each graph and try to identify those in G with those in H.

hello
thanx i know about the dgrees but i still don't know how to determine that somtime the degree fo the vertices does tell you a bout that... so i know step by step details in order to know all possiblities... i appreciate your help
thanx
 
  • #4
Very well, do you know what "isomorphic" MEANS? Notice that cristo did not just say "work out the degree" he also said "try to identify those in G with those in H". What have you done toward that? What is the degree of each point in G and each point in H?
 
  • #5
okey that's what i have but i still need some one to explain that in steps

For G this graph is made of
a 3-cycle agc,
a 4-cycle hdbf.
For H this graph is made of
a 7-cycle 2583647. C

so G and H are not isomorphic

i am not sure if this iright or wrong and the same time i need some explanation so i can be sure for what i am doing

thanc
 
  • #6
You've not answered Halls' question: what does isomorphic mean? What is the degree of each vertex of G and each vertex of H?

Also, I don't understand your notation: what, for example, does the cycle agc mean? I would presume it to mean an edge from a to g, another from g to c and a third from c to a; but there is no edge from a to g in the graph G! Please explain your notation.
 
  • #7
Isomorphic means same shaped,,,,,,,, now i need explanation

i tried to follow some examples with no luck
 
  • #8
hyderman said:
Isomorphic means same shaped,,,,,,,, now i need explanation

i tried to follow some examples with no luck

You need to be more precise-- "same shaped" is not a mathematical definition of two isomorphic graphs.

Have you read the rest of my last post? Please answer my questions-- I will not tell you the answer without you putting some effort into solving the problem.
 
  • #9
cristo said:
You need to be more precise-- "same shaped" is not a mathematical definition of two isomorphic graphs.

Have you read the rest of my last post? Please answer my questions-- I will not tell you the answer without you putting some effort into solving the problem.


isomorphic:

Two graphs are isomorphic if there is a one-to-one correspondence between their vertices and there is an edge between two vertices of one graph if and only if there is an edge between the two corresponding vertices in the other graph.

G:

a-5 degrees
b-5
.

.
h- 5


for
H:

1-6 DEGREES
2-4
3-5
4-5
...
,,,
8-5 DEGREES
 

1. How do you determine if two graphs are isomorphic?

The easiest way to determine if two graphs, G and H, are isomorphic is to check if they have the same number of vertices and edges. If they do, you can then compare their adjacency matrices to see if they have the same structure.

2. What is an adjacency matrix?

An adjacency matrix is a square matrix that represents a graph by listing all of its vertices on both axes and indicating which vertices are connected by an edge. This matrix can be used to compare the structures of two graphs.

3. Can two isomorphic graphs have different numbers of edges?

No, two isomorphic graphs must have the same number of edges. This is because isomorphic graphs have the same structure, and the number of edges is a crucial part of a graph's structure.

4. Are there any other methods for determining if two graphs are isomorphic?

Yes, there are other methods such as the path-based method, the degree sequence method, and the automorphism method. These methods involve comparing different properties of the graphs to see if they are the same.

5. What is the significance of determining if two graphs are isomorphic?

Determining if two graphs are isomorphic can help us understand the relationship between them and can also help us solve problems involving one graph by using the properties of the other. It is also important in various fields such as computer science, chemistry, and genetics.

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