1 citations · 1 across the 6 of their papers we have counts for
7 papers
Towards a classification of -homogeneous distance-regular graphs with positive intersection number
Jack H. Koolen, Mamoon Abdullah, Brhane Gebremichel +1
Let be a graph with diameter at least two. Then is said to be -homogeneous (in the sense of Nomura) whenever for every pair of adjacent vertices and in , the…
Distance-regular graphs with a few -distance eigenvalues
Mamoon Abdullah, Brhane Gebremichel, Sakander Hayat +1
In this paper we study when the -distance matrix of a distance-regular graph has few distinct eigenvalues. We mainly concentrate on diameter 3.
Distance-regular graphs with exactly one positive -distance eigenvalue
Jack H. Koolen, Mamoon Abdullah, Brhane Gebremichel +1
In this paper, we study the -distance matrix for a distance-regular graph and show that the -distance matrix of a distance-regular graph with classical parameters ($D, q, α,…
There does not exist a strongly regular graph with parameters
Jack H. Koolen, Brhane Gebremichel
In this paper we show that there does not exist a strongly regular graph with parameters .
Sesqui-regular graphs with smallest eigenvalue at least
Qianqian Yang, Brhane Gebremichel, Masood Ur Rehman +2
Koolen et al. showed that if a graph with smallest eigenvalue at least has large minimal valency, then it is -integrable. In this paper, we will focus on the sesqui-regular…
Two characterizations of the grid graphs
Brhane Gebremichel, Meng-Yue Cao, Jack H. Koolen
In this paper we give two characterizations of the -grid graphs as co-edge-regular graphs with four distinct eigenvalues.
Sesqui-regular graphs with fixed smallest eigenvalue
Jack H. Koolen, Brhane Gebremichel, Jae Young Yang +1
Let be an integer. For strongly regular graphs with parameters and smallest eigenvalue , Neumaier gave two bounds on by using algebraic property of s…