English

Girth and Laplacian eigenvalue distribution

Combinatorics 2025-06-03 v1

Abstract

Let GG be a connected graph of order nn with girth gg. For k=1,,min{g1,ng}k=1,\dots,\min\{g-1, n-g\}, let n(G,k)n(G,k) be the number of Laplacian eigenvalues (counting multiplicities) of GG that fall inside the interval [ngk+4,n][n-g-k+4,n]. We prove that if g4g\ge 4, then n(G,k)ng. n(G,k)\le n-g. Those graphs achieving the bound for k=1,2k=1,2 are determined. We also determine the graphs GG with g=3g=3 such that n(G,k)=n1,n2,n3n(G,k)=n-1, n-2, n-3.

Keywords

Cite

@article{arxiv.2506.00921,
  title  = {Girth and Laplacian eigenvalue distribution},
  author = {Leyou Xu and Bo Zhou},
  journal= {arXiv preprint arXiv:2506.00921},
  year   = {2025}
}
R2 v1 2026-07-01T02:52:59.300Z