English

Biregular graphs with three eigenvalues

Combinatorics 2016-05-03 v2

Abstract

We consider nonregular graphs having precisely three distinct eigenvalues. The focus is mainly on the case of graphs having two distinct valencies and our results include constructions of new examples, structure theorems, valency constraints, and a classification of certain special families of such graphs. We also present a new example of a graph with three valencies and three eigenvalues of which there are currently only finitely many known examples.

Keywords

Cite

@article{arxiv.1412.6971,
  title  = {Biregular graphs with three eigenvalues},
  author = {Xi-Ming Cheng and Alexander L. Gavrilyuk and Gary R. W. Greaves and Jack H. Koolen},
  journal= {arXiv preprint arXiv:1412.6971},
  year   = {2016}
}

Comments

28 pages

R2 v1 2026-06-22T07:40:36.299Z