English

Adjacency spectral radius and H-factors in 1-binding graphs

Combinatorics 2025-08-07 v2

Abstract

Let GG be a graph, and let H:V(G){{1},{0,2}}H:V(G)\longrightarrow\{\{1\},\{0,2\}\} be a set-valued function. Hence, H(v)H(v) equals {1}\{1\} or {0,2}\{0,2\} for any vV(G)v\in V(G). We let H1(1)={v:vV(G) \mboxand H(v)=1}. H^{-1}(1)=\{v: v\in V(G) \ \mbox{and} \ H(v)=1\}. An HH-factor of GG is a spanning subgraph FF of GG such that dF(v)H(v)d_F(v)\in H(v) for each vV(G)v\in V(G). Lu and Kano showed a characterization for the existence of an HH-factor in a graph [Characterization of 1-tough graphs using factors, Discrete Math. 343 (2020) 111901]. Let A(G)A(G) and ρ(G)\rho(G) denote the adjacency matrix and the adjacency spectral radius of GG, respectively. By using Lu and Kano's result, we pose a sufficient condition with respect to the adjacency spectral radius to guarantee the existence of an HH-factor in a 1-binding graph. In this paper, we prove that if a connected 1-binding graph GG of order n11n\geq11 satisfies ρ(G)ρ(K1(Kn4K2K1))\rho(G)\geq\rho(K_1\vee(K_{n-4}\cup K_2\cup K_1)), then GG has an HH-factor for each H:V(G){{1},{0,2}}H:V(G)\longrightarrow\{\{1\},\{0,2\}\} with H1(1)H^{-1}(1) even, unless G=K1(Kn4K2K1)G=K_1\vee(K_{n-4}\cup K_2\cup K_1).

Keywords

Cite

@article{arxiv.2506.20273,
  title  = {Adjacency spectral radius and H-factors in 1-binding graphs},
  author = {Sizhong Zhou and Tao Zhang and Zhiren Sun},
  journal= {arXiv preprint arXiv:2506.20273},
  year   = {2025}
}

Comments

9 pages

R2 v1 2026-07-01T03:32:46.001Z