Skip to main content

All Questions

Filter by
Sorted by
Tagged with
5 votes
0 answers
513 views

Computing adjacency matrix eigenvalues by counting closed walks

Let $G$ be a finite undirected graph. A closed walk in $G$ is a walk from any vertex of $G$ to itself. It is relatively straightforward to show that the total number of closed walks of length $k$ in $...
Sam Hopkins's user avatar
  • 24.2k
24 votes
6 answers
2k views

Factorization of the characteristic polynomial of the adjacency matrix of a graph

Let $G$ be a regular graph of valence $d$ with finitely many vertices, let $A_G$ be its adjacency matrix, and let $$P_G(X)=\det(X-A_G)\in\mathbb{Z}[X]$$ be the adjacency polynomial of $G$, i.e., the ...
Joe Silverman's user avatar
4 votes
1 answer
207 views

Digraphs with unique walk of length $k$ between any two vertices

Let $G$ be a digraph such that there is an unique directed walk of length $k$ between any two vertices. Equivalently, if $A$ is the adjacency matrix of $G$, then $A^k$ is the matrix with all entries $...
Antoine Labelle's user avatar
1 vote
1 answer
847 views

Do there exist graphs whose adjacency matrix is positive semi-definite? [closed]

If so, could you provide examples and specify the conditions under which this occurs? Thank you in advance
DanteAligante's user avatar
2 votes
2 answers
234 views

Adjacency matrix of total graph

Is there a nice way of relating the adjacency, incidence , Laplacian matrices and other matrices associated to a graph of a total graph with its original graph, or, say, at least relating that of the ...
vidyarthi's user avatar
  • 2,089