1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Determine if G and H are isomorphic

  1. Mar 15, 2007 #1
    please help by explainig in steps thanx much


    Determine if G and H are isomorphic. Justify your answer



    [​IMG]
     
    Last edited: Mar 15, 2007
  2. jcsd
  3. Mar 16, 2007 #2

    cristo

    User Avatar
    Staff Emeritus
    Science Advisor

    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.
     
  4. Mar 16, 2007 #3
    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
     
  5. Mar 16, 2007 #4

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    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?
     
  6. Mar 16, 2007 #5
    okey thats 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
     
  7. Mar 16, 2007 #6

    cristo

    User Avatar
    Staff Emeritus
    Science Advisor

    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.
     
  8. Mar 16, 2007 #7
    Isomorphic means same shaped,,,,,,,, now i need explanation

    i tried to follow some examples with no luck
     
  9. Mar 16, 2007 #8

    cristo

    User Avatar
    Staff Emeritus
    Science Advisor

    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.
     
  10. Mar 16, 2007 #9

    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
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?