To find the number of spanning trees of a graph given its adjacency matrix












-2














A graph $G$ has the following adjacency matrix:



$$ begin{pmatrix}
0 & 0 & 0 & 0 & 1 & 1 & 1 & 1 \
0 & 0 & 0 & 0 & 0 & 1 & 1 & 1 \
0 & 0 & 0 & 1 & 0 & 1 & 1 & 1 \
0 & 0 & 1 & 0 & 0 & 0 & 0 & 1 \
1 & 0 & 0 & 0 & 0 & 1 & 0 & 0 \
1 & 1 & 1 & 0 & 0 & 0 & 0 & 0 \
1 & 1 & 1 & 0 & 0 & 0 & 0 & 0 \
1 & 1 & 1 & 1 & 0 & 0 & 0 & 0 \
end{pmatrix} $$



I have created a Laplacian matrix from that adjacency matrix, and I know that the determinant of the Laplacian will give you the result, however, I doubt that our prof would make us find the determinant of an 8x8 matrix and I've read around that you can minimize the size of matrix (by deleting corresponding col & rows), though I don't see how I could reduce the size of my 8x8 Laplacian matrix without it losing its unique graph identity?










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  • The missing entry is 1, sorry, forgot to clarify that. Do you have anything to say in regards to the question I asked though?
    – DevAllanPer
    Dec 7 at 16:31








  • 3




    Could you include the Laplacian matrix in question?
    – coffeemath
    Dec 7 at 19:08










  • I think there's a typo on that matrix, but anyhow im sure my understanding is correct. The number of spanning trees should be equal to the determinant of the 7x7 Laplacian matrix (7x7 cuz you can remove any row and column)
    – DevAllanPer
    Dec 9 at 16:32










  • As the author of the Question, you need to assume responsibility for stating a problem (that you want help with) correctly. Readers depend on you to be the expert on what exactly is being asked, so that they can supply helpful Answers. As promised, I edited the Question to show how math notation can be used on the site (see this brief introduction and its links for more information). At a minimum you should supply the Laplacian matrix that you created and explain what difficulty you encountered proceeding from there.
    – hardmath
    Dec 10 at 18:14










  • i already took the exam. thanks anyway
    – DevAllanPer
    Dec 12 at 2:04
















-2














A graph $G$ has the following adjacency matrix:



$$ begin{pmatrix}
0 & 0 & 0 & 0 & 1 & 1 & 1 & 1 \
0 & 0 & 0 & 0 & 0 & 1 & 1 & 1 \
0 & 0 & 0 & 1 & 0 & 1 & 1 & 1 \
0 & 0 & 1 & 0 & 0 & 0 & 0 & 1 \
1 & 0 & 0 & 0 & 0 & 1 & 0 & 0 \
1 & 1 & 1 & 0 & 0 & 0 & 0 & 0 \
1 & 1 & 1 & 0 & 0 & 0 & 0 & 0 \
1 & 1 & 1 & 1 & 0 & 0 & 0 & 0 \
end{pmatrix} $$



I have created a Laplacian matrix from that adjacency matrix, and I know that the determinant of the Laplacian will give you the result, however, I doubt that our prof would make us find the determinant of an 8x8 matrix and I've read around that you can minimize the size of matrix (by deleting corresponding col & rows), though I don't see how I could reduce the size of my 8x8 Laplacian matrix without it losing its unique graph identity?










share|cite|improve this question
























  • The missing entry is 1, sorry, forgot to clarify that. Do you have anything to say in regards to the question I asked though?
    – DevAllanPer
    Dec 7 at 16:31








  • 3




    Could you include the Laplacian matrix in question?
    – coffeemath
    Dec 7 at 19:08










  • I think there's a typo on that matrix, but anyhow im sure my understanding is correct. The number of spanning trees should be equal to the determinant of the 7x7 Laplacian matrix (7x7 cuz you can remove any row and column)
    – DevAllanPer
    Dec 9 at 16:32










  • As the author of the Question, you need to assume responsibility for stating a problem (that you want help with) correctly. Readers depend on you to be the expert on what exactly is being asked, so that they can supply helpful Answers. As promised, I edited the Question to show how math notation can be used on the site (see this brief introduction and its links for more information). At a minimum you should supply the Laplacian matrix that you created and explain what difficulty you encountered proceeding from there.
    – hardmath
    Dec 10 at 18:14










  • i already took the exam. thanks anyway
    – DevAllanPer
    Dec 12 at 2:04














-2












-2








-2


1





A graph $G$ has the following adjacency matrix:



$$ begin{pmatrix}
0 & 0 & 0 & 0 & 1 & 1 & 1 & 1 \
0 & 0 & 0 & 0 & 0 & 1 & 1 & 1 \
0 & 0 & 0 & 1 & 0 & 1 & 1 & 1 \
0 & 0 & 1 & 0 & 0 & 0 & 0 & 1 \
1 & 0 & 0 & 0 & 0 & 1 & 0 & 0 \
1 & 1 & 1 & 0 & 0 & 0 & 0 & 0 \
1 & 1 & 1 & 0 & 0 & 0 & 0 & 0 \
1 & 1 & 1 & 1 & 0 & 0 & 0 & 0 \
end{pmatrix} $$



I have created a Laplacian matrix from that adjacency matrix, and I know that the determinant of the Laplacian will give you the result, however, I doubt that our prof would make us find the determinant of an 8x8 matrix and I've read around that you can minimize the size of matrix (by deleting corresponding col & rows), though I don't see how I could reduce the size of my 8x8 Laplacian matrix without it losing its unique graph identity?










share|cite|improve this question















A graph $G$ has the following adjacency matrix:



$$ begin{pmatrix}
0 & 0 & 0 & 0 & 1 & 1 & 1 & 1 \
0 & 0 & 0 & 0 & 0 & 1 & 1 & 1 \
0 & 0 & 0 & 1 & 0 & 1 & 1 & 1 \
0 & 0 & 1 & 0 & 0 & 0 & 0 & 1 \
1 & 0 & 0 & 0 & 0 & 1 & 0 & 0 \
1 & 1 & 1 & 0 & 0 & 0 & 0 & 0 \
1 & 1 & 1 & 0 & 0 & 0 & 0 & 0 \
1 & 1 & 1 & 1 & 0 & 0 & 0 & 0 \
end{pmatrix} $$



I have created a Laplacian matrix from that adjacency matrix, and I know that the determinant of the Laplacian will give you the result, however, I doubt that our prof would make us find the determinant of an 8x8 matrix and I've read around that you can minimize the size of matrix (by deleting corresponding col & rows), though I don't see how I could reduce the size of my 8x8 Laplacian matrix without it losing its unique graph identity?







matrices graph-theory determinant graph-laplacian






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share|cite|improve this question













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share|cite|improve this question








edited Dec 10 at 19:58









hardmath

28.7k94994




28.7k94994










asked Dec 7 at 16:11









DevAllanPer

1296




1296












  • The missing entry is 1, sorry, forgot to clarify that. Do you have anything to say in regards to the question I asked though?
    – DevAllanPer
    Dec 7 at 16:31








  • 3




    Could you include the Laplacian matrix in question?
    – coffeemath
    Dec 7 at 19:08










  • I think there's a typo on that matrix, but anyhow im sure my understanding is correct. The number of spanning trees should be equal to the determinant of the 7x7 Laplacian matrix (7x7 cuz you can remove any row and column)
    – DevAllanPer
    Dec 9 at 16:32










  • As the author of the Question, you need to assume responsibility for stating a problem (that you want help with) correctly. Readers depend on you to be the expert on what exactly is being asked, so that they can supply helpful Answers. As promised, I edited the Question to show how math notation can be used on the site (see this brief introduction and its links for more information). At a minimum you should supply the Laplacian matrix that you created and explain what difficulty you encountered proceeding from there.
    – hardmath
    Dec 10 at 18:14










  • i already took the exam. thanks anyway
    – DevAllanPer
    Dec 12 at 2:04


















  • The missing entry is 1, sorry, forgot to clarify that. Do you have anything to say in regards to the question I asked though?
    – DevAllanPer
    Dec 7 at 16:31








  • 3




    Could you include the Laplacian matrix in question?
    – coffeemath
    Dec 7 at 19:08










  • I think there's a typo on that matrix, but anyhow im sure my understanding is correct. The number of spanning trees should be equal to the determinant of the 7x7 Laplacian matrix (7x7 cuz you can remove any row and column)
    – DevAllanPer
    Dec 9 at 16:32










  • As the author of the Question, you need to assume responsibility for stating a problem (that you want help with) correctly. Readers depend on you to be the expert on what exactly is being asked, so that they can supply helpful Answers. As promised, I edited the Question to show how math notation can be used on the site (see this brief introduction and its links for more information). At a minimum you should supply the Laplacian matrix that you created and explain what difficulty you encountered proceeding from there.
    – hardmath
    Dec 10 at 18:14










  • i already took the exam. thanks anyway
    – DevAllanPer
    Dec 12 at 2:04
















The missing entry is 1, sorry, forgot to clarify that. Do you have anything to say in regards to the question I asked though?
– DevAllanPer
Dec 7 at 16:31






The missing entry is 1, sorry, forgot to clarify that. Do you have anything to say in regards to the question I asked though?
– DevAllanPer
Dec 7 at 16:31






3




3




Could you include the Laplacian matrix in question?
– coffeemath
Dec 7 at 19:08




Could you include the Laplacian matrix in question?
– coffeemath
Dec 7 at 19:08












I think there's a typo on that matrix, but anyhow im sure my understanding is correct. The number of spanning trees should be equal to the determinant of the 7x7 Laplacian matrix (7x7 cuz you can remove any row and column)
– DevAllanPer
Dec 9 at 16:32




I think there's a typo on that matrix, but anyhow im sure my understanding is correct. The number of spanning trees should be equal to the determinant of the 7x7 Laplacian matrix (7x7 cuz you can remove any row and column)
– DevAllanPer
Dec 9 at 16:32












As the author of the Question, you need to assume responsibility for stating a problem (that you want help with) correctly. Readers depend on you to be the expert on what exactly is being asked, so that they can supply helpful Answers. As promised, I edited the Question to show how math notation can be used on the site (see this brief introduction and its links for more information). At a minimum you should supply the Laplacian matrix that you created and explain what difficulty you encountered proceeding from there.
– hardmath
Dec 10 at 18:14




As the author of the Question, you need to assume responsibility for stating a problem (that you want help with) correctly. Readers depend on you to be the expert on what exactly is being asked, so that they can supply helpful Answers. As promised, I edited the Question to show how math notation can be used on the site (see this brief introduction and its links for more information). At a minimum you should supply the Laplacian matrix that you created and explain what difficulty you encountered proceeding from there.
– hardmath
Dec 10 at 18:14












i already took the exam. thanks anyway
– DevAllanPer
Dec 12 at 2:04




i already took the exam. thanks anyway
– DevAllanPer
Dec 12 at 2:04















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