English

Diameter vs Laplacian eigenvalue distribution

Combinatorics 2024-06-04 v2

Abstract

Let GG be a simple graph of order nn. It is known that any Laplacian eigenvalue of GG belongs to the interval [0,n][0,n]. For an interval I[0,n]I\subseteq [0, n], denote by mGIm_GI the number of Laplacian eigenvalues of GG in II, counted with multiplicity. When GG is connected, known results on the Laplacian eigenvalue distribution related to the diameter dd of GG include: mG[nd+2,n]ndm_G[n-d+2,n]\le n-d if 2dn32\le d\le n-3 and mG[nd+1,n]nd+1m_G[n-d+1,n]\le n-d+1 if 1dn31\le d\le n-3. In this paper, we show that mG[nd,n]nd+2m_G[n-d,n]\le n-d+2 if 2dn42\le d\le n-4, and mG[n2d+4,n]n2m_G[n-2d+4,n]\le n-2 if 2dn22\le d\le \lfloor\frac{n}{2} \rfloor.

Keywords

Cite

@article{arxiv.2401.03777,
  title  = {Diameter vs Laplacian eigenvalue distribution},
  author = {Leyou Xu and Bo Zhou},
  journal= {arXiv preprint arXiv:2401.03777},
  year   = {2024}
}
R2 v1 2026-06-28T14:11:01.597Z