W. Haemers

activity

20082026

most citedRegular graphs with maximal energy per vertex

9 citations · 16 across the 23 of their papers we have counts for

collaborators

Showing 2021Show all

4 papers · 1 filter

math.CO2021

On signed graphs with at most two eigenvalues unequal to $\pm 1$

Willem H. Haemers, Hatice Topcu

We present the first steps towards the determination of the signed graphs for which the adjacency matrix has all but at most two eigenvalues equal to 1 or -1. Here we deal with the…

math.CO2021

Graph toughness from Laplacian eigenvalues

Xiaofeng Gu, Willem H. Haemers

The toughness $t (G)$ of a graph $G = (V, E)$ is defined as $t (G) = min {\frac{∣ S ∣}{c ( G - S )}}$ , in which the minimum is taken over all $S \subset V$ such that $G - S$ is disconnected, wher…

math.CO2021

Hoffman's ratio bound

Willem H. Haemers

Hoffman's ratio bound is an upper bound for the independence number of a regular graph in terms of the eigenvalues of the adjacency matrix. The bound has proved to be very useful a…

math.CO2021

Spectra of strongly Deza graphs

Saieed Akbari, Willem H. Haemers, Mohammad Ali Hosseinzadeh +3

A Deza graph $G$ with parameters $(n, k, b, a)$ is a $k$ -regular graph with $n$ vertices such that any two distinct vertices have $b$ or $a$ common neighbours. The children $G_{A}$ and…

On signed graphs with at most two eigenvalues unequal to ±1

Graph toughness from Laplacian eigenvalues

Hoffman's ratio bound

Spectra of strongly Deza graphs

On signed graphs with at most two eigenvalues unequal to $\pm 1$