Eigenvalues of the Laplacian of the directed De Bruijn graphDoes graph asymmetry imply all eigenvalues of the graph Laplacian are simple?Can the friendship graph be determind by its adjacency spectrum?Extreme Laplacian eigenvaluesConnection between eigenvalues of matrix and its Laplacian.Spectral Graph TheoryWhen does the normalized graph Laplacian have eigenvalue 1?Hashimoto Matrix (Non-backtracking operator) and the Graph LaplacianDirected graph Laplacian with exactly one negative eigenvalueSpectra of undirected $d$-regular graphsLocal-Global Principle in Graph Spectrum

Eigenvalues of the Laplacian of the directed De Bruijn graph


Does graph asymmetry imply all eigenvalues of the graph Laplacian are simple?Can the friendship graph be determind by its adjacency spectrum?Extreme Laplacian eigenvaluesConnection between eigenvalues of matrix and its Laplacian.Spectral Graph TheoryWhen does the normalized graph Laplacian have eigenvalue 1?Hashimoto Matrix (Non-backtracking operator) and the Graph LaplacianDirected graph Laplacian with exactly one negative eigenvalueSpectra of undirected $d$-regular graphsLocal-Global Principle in Graph Spectrum













5












$begingroup$


We will denote by $DB(n,k)$ the directed De Bruijn graph, which is a digraph whose vertices are elements of $0,1,dots,k-1^n$, and $sigma_1cdots sigma_n$ is connected to $tau_1cdots tau_n$ if and only if $sigma_i=tau_i+1$ for every $i=1,dots,n-1$.



We would like to calculate the spectrum of the Laplacian matrix of $DB(n,k)$. Note that since $DB(n,k)$ is $k$-regular, then $lambda in Spec(L_DB(n,k))$ if and only if $k-lambda in Spec(A_DB(n,k))$, so we can calculate the eigenvalues of the Laplacian matrix from the eigenvalues of the Adjacency matrix.



We found the following article on the subject, but it only calculates the spectrum of the underlining undirected graph of the De Bruijn graph:



https://core.ac.uk/download/pdf/82810454.pdf



Thanks!










share|cite|improve this question











$endgroup$
















    5












    $begingroup$


    We will denote by $DB(n,k)$ the directed De Bruijn graph, which is a digraph whose vertices are elements of $0,1,dots,k-1^n$, and $sigma_1cdots sigma_n$ is connected to $tau_1cdots tau_n$ if and only if $sigma_i=tau_i+1$ for every $i=1,dots,n-1$.



    We would like to calculate the spectrum of the Laplacian matrix of $DB(n,k)$. Note that since $DB(n,k)$ is $k$-regular, then $lambda in Spec(L_DB(n,k))$ if and only if $k-lambda in Spec(A_DB(n,k))$, so we can calculate the eigenvalues of the Laplacian matrix from the eigenvalues of the Adjacency matrix.



    We found the following article on the subject, but it only calculates the spectrum of the underlining undirected graph of the De Bruijn graph:



    https://core.ac.uk/download/pdf/82810454.pdf



    Thanks!










    share|cite|improve this question











    $endgroup$














      5












      5








      5





      $begingroup$


      We will denote by $DB(n,k)$ the directed De Bruijn graph, which is a digraph whose vertices are elements of $0,1,dots,k-1^n$, and $sigma_1cdots sigma_n$ is connected to $tau_1cdots tau_n$ if and only if $sigma_i=tau_i+1$ for every $i=1,dots,n-1$.



      We would like to calculate the spectrum of the Laplacian matrix of $DB(n,k)$. Note that since $DB(n,k)$ is $k$-regular, then $lambda in Spec(L_DB(n,k))$ if and only if $k-lambda in Spec(A_DB(n,k))$, so we can calculate the eigenvalues of the Laplacian matrix from the eigenvalues of the Adjacency matrix.



      We found the following article on the subject, but it only calculates the spectrum of the underlining undirected graph of the De Bruijn graph:



      https://core.ac.uk/download/pdf/82810454.pdf



      Thanks!










      share|cite|improve this question











      $endgroup$




      We will denote by $DB(n,k)$ the directed De Bruijn graph, which is a digraph whose vertices are elements of $0,1,dots,k-1^n$, and $sigma_1cdots sigma_n$ is connected to $tau_1cdots tau_n$ if and only if $sigma_i=tau_i+1$ for every $i=1,dots,n-1$.



      We would like to calculate the spectrum of the Laplacian matrix of $DB(n,k)$. Note that since $DB(n,k)$ is $k$-regular, then $lambda in Spec(L_DB(n,k))$ if and only if $k-lambda in Spec(A_DB(n,k))$, so we can calculate the eigenvalues of the Laplacian matrix from the eigenvalues of the Adjacency matrix.



      We found the following article on the subject, but it only calculates the spectrum of the underlining undirected graph of the De Bruijn graph:



      https://core.ac.uk/download/pdf/82810454.pdf



      Thanks!







      co.combinatorics graph-theory spectral-graph-theory enumerative-combinatorics






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      share|cite|improve this question













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      edited Apr 23 at 17:50









      Fedor Petrov

      52.5k6123241




      52.5k6123241










      asked Apr 23 at 16:58









      Serge the ToasterSerge the Toaster

      592




      592




















          2 Answers
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          4












          $begingroup$

          I believe that for $p$ prime $DB(m,p)$ has one 0 eigenvalue (this is easy to check), and the other eigenvalues are all equal to $p$. This is something that we observed while working on https://arxiv.org/abs/1405.0113, but didn't try to prove (should not be too hard I guess, using a decription of $DB(m,p)$ as the line graph of $DB(m-1,p)$, and then induction).






          share|cite|improve this answer











          $endgroup$




















            4












            $begingroup$

            The computation for $k=2$ appears (among other places) on pp. 158--159 of my book Algebraic Combinatorics, second edition. The computation for arbitrary $k$ is completely analogous. Dima Pasechnik is correct that there is one eigenvalue equal to 0, and all the others are equal to $k$.






            share|cite|improve this answer









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              2 Answers
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              2 Answers
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              4












              $begingroup$

              I believe that for $p$ prime $DB(m,p)$ has one 0 eigenvalue (this is easy to check), and the other eigenvalues are all equal to $p$. This is something that we observed while working on https://arxiv.org/abs/1405.0113, but didn't try to prove (should not be too hard I guess, using a decription of $DB(m,p)$ as the line graph of $DB(m-1,p)$, and then induction).






              share|cite|improve this answer











              $endgroup$

















                4












                $begingroup$

                I believe that for $p$ prime $DB(m,p)$ has one 0 eigenvalue (this is easy to check), and the other eigenvalues are all equal to $p$. This is something that we observed while working on https://arxiv.org/abs/1405.0113, but didn't try to prove (should not be too hard I guess, using a decription of $DB(m,p)$ as the line graph of $DB(m-1,p)$, and then induction).






                share|cite|improve this answer











                $endgroup$















                  4












                  4








                  4





                  $begingroup$

                  I believe that for $p$ prime $DB(m,p)$ has one 0 eigenvalue (this is easy to check), and the other eigenvalues are all equal to $p$. This is something that we observed while working on https://arxiv.org/abs/1405.0113, but didn't try to prove (should not be too hard I guess, using a decription of $DB(m,p)$ as the line graph of $DB(m-1,p)$, and then induction).






                  share|cite|improve this answer











                  $endgroup$



                  I believe that for $p$ prime $DB(m,p)$ has one 0 eigenvalue (this is easy to check), and the other eigenvalues are all equal to $p$. This is something that we observed while working on https://arxiv.org/abs/1405.0113, but didn't try to prove (should not be too hard I guess, using a decription of $DB(m,p)$ as the line graph of $DB(m-1,p)$, and then induction).







                  share|cite|improve this answer














                  share|cite|improve this answer



                  share|cite|improve this answer








                  edited Apr 23 at 17:48

























                  answered Apr 23 at 17:36









                  Dima PasechnikDima Pasechnik

                  9,46311953




                  9,46311953





















                      4












                      $begingroup$

                      The computation for $k=2$ appears (among other places) on pp. 158--159 of my book Algebraic Combinatorics, second edition. The computation for arbitrary $k$ is completely analogous. Dima Pasechnik is correct that there is one eigenvalue equal to 0, and all the others are equal to $k$.






                      share|cite|improve this answer









                      $endgroup$

















                        4












                        $begingroup$

                        The computation for $k=2$ appears (among other places) on pp. 158--159 of my book Algebraic Combinatorics, second edition. The computation for arbitrary $k$ is completely analogous. Dima Pasechnik is correct that there is one eigenvalue equal to 0, and all the others are equal to $k$.






                        share|cite|improve this answer









                        $endgroup$















                          4












                          4








                          4





                          $begingroup$

                          The computation for $k=2$ appears (among other places) on pp. 158--159 of my book Algebraic Combinatorics, second edition. The computation for arbitrary $k$ is completely analogous. Dima Pasechnik is correct that there is one eigenvalue equal to 0, and all the others are equal to $k$.






                          share|cite|improve this answer









                          $endgroup$



                          The computation for $k=2$ appears (among other places) on pp. 158--159 of my book Algebraic Combinatorics, second edition. The computation for arbitrary $k$ is completely analogous. Dima Pasechnik is correct that there is one eigenvalue equal to 0, and all the others are equal to $k$.







                          share|cite|improve this answer












                          share|cite|improve this answer



                          share|cite|improve this answer










                          answered Apr 23 at 19:46









                          Richard StanleyRichard Stanley

                          29.4k9118191




                          29.4k9118191



























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