English

Integral Laplacian graphs with a unique double Laplacian eigenvalue, II

Combinatorics 2025-07-01 v1

Abstract

The set S{i,j}nm={0,1,2,,m1,m,m,m+1,,n1,n}{i,j},0<i<jnS_{\{i,j\}_{n}^{m}}=\{0,1,2,\ldots,m-1,m,m,m+1,\ldots,n-1,n\}\setminus\{i,j\},\quad 0<i<j\leqslant n, is called Laplacian realizable if there exists a simple connected graph GG whose Laplacian spectrum is S{i,j}nmS_{\{i,j\}_{n}^{m}}. In this case, the graph GG is said to realize S{i,j}nmS_{\{i,j\}_{n}^{m}}. In this paper, we completely describe graphs realizing the sets S{i,j}nmS_{\{i,j\}_{n}^{m}} with m=1,2m=1,2 and determine the structure of these graphs.

Keywords

Cite

@article{arxiv.2307.07275,
  title  = {Integral Laplacian graphs with a unique double Laplacian eigenvalue, II},
  author = {Abdul Hameed and Mikhail Tyaglov},
  journal= {arXiv preprint arXiv:2307.07275},
  year   = {2025}
}

Comments

14 pages

R2 v1 2026-06-28T11:30:22.535Z