Skip to main content

All Questions

Filter by
Sorted by
Tagged with
0 votes
0 answers
36 views

A class of directed graph, when their minimal polynomial of the adjacency matrix matches the characteristic polynomial

We consider an unweighted directed simple graph, $G$, with a Hamiltonian cycle. Q. Assume that the adjacency matrix of $G$ is non-singular. Do the characteristic and minimal polynomials of the ...
ABB's user avatar
  • 4,058
1 vote
2 answers
198 views

Topology of directed graph $G$ with non-singular adjacency matrix

Given a directed graph $G$ with non-singular adjacency matrix, Q. Is there a directed subgraph $H$ in $G$ that can be represented as the union of disjoint cycles such that $H$ contains all nodes of $...
ABB's user avatar
  • 4,058
1 vote
1 answer
143 views

Eigenvalues of directed graph with one outward edge for each vertex

I am concerned with unweighted directed graphs where each node contains exactly one edge pointing to another node, which could be itself. In other words, each row of the adjacency matrix contains one ...
user3433489's user avatar
1 vote
0 answers
112 views

Digraphs with same number of semiwalks

This is a follow-up question to Characterisation of walk-equivalent digraphs. Question: Do there exists two directed graphs $G$ and $H$ consisting of the same number ($n$) of vertices, such that \...
Sirolf's user avatar
  • 493
1 vote
1 answer
138 views

Characterisation of walk-equivalent digraphs

Setting Let $G=(V,E)$ be an undirected graph. A walk $\pi$ in $G$ of length $k$ is a sequence of $k+1$ vertices $v_1,\ldots,v_{k+1}$ such that for each $i\in[1,k]$, $\{v_i,v_{i+1}\}\in E$. Let $H=(W,F)...
Sirolf's user avatar
  • 493
2 votes
1 answer
122 views

Two cospectral (normal) digraphs which are not orthogonal similar

Preliminaries A complex matrix $A$ is normal when $A$ and $A^*$ commute. A real matrix $A$ is normal when $A$ and $A^t$ commute. Two complex matrices $A$ and $B$ are said to be unitary similar if ...
Sirolf's user avatar
  • 493