English

Distribution of signless Laplacian eigenvalues and degree sequence

Combinatorics 2026-05-28 v1 Spectral Theory

Abstract

Let GG be a graph of order nn with degree sequence d1dnd_1 \geq \cdots \geq d_{n}. Let mGIm_{G}I be the number of signless Laplacian eigenvalues in an interval II. In this paper, we characterize the distribution of the signless Laplacian eigenvalues in terms of the degree sequence of a graph within specific subintervals of [0,2n2].[0, \, 2n-2]. We determine all graphs GG such that mG[dn,2n2]2,  mG[dn1,2n2]=1,  mG[0,d1]2.m_{G}[d_n, 2n-2] \leq 2, \; m_{G}[d_{n-1}, 2n-2] = 1, \; m_{G}[0, d_1] \le 2. We also prove that there is no graph such that mG[0,d3]=1m_{G}[0, d_3]=1. In addition, we obtain all disconnected graphs such that mG[0,d1]=3m_{G}[0, d_1] = 3. Finally, we propose two open problems for future research.

Keywords

Cite

@article{arxiv.2605.27405,
  title  = {Distribution of signless Laplacian eigenvalues and degree sequence},
  author = {Saieed Akbari and M. Darougheh and L. S. de Lima and D. Tracina},
  journal= {arXiv preprint arXiv:2605.27405},
  year   = {2026}
}
R2 v1 2026-07-22T07:35:13.576Z