English

Saturation numbers of $K_{2}\vee P_{k}$

Combinatorics 2025-11-26 v1

Abstract

A graph GG is called HH-saturated if GG contains no copy of HH, but G+eG+e contains a copy of HH for any edge eE(G)e\in E(\overline{G}). The saturation number of HH is the minimum number of edges in an HH-saturated graph of order nn, denoted by sat(n,H)sat(n,H). In this paper, we investigate sat(n,K2Pk)sat(n,K_{2}\vee P_{k}), where k3k\geq 3. Let aka_k be an integer, defined as follows: ak=ka_k=k for 3k53\leq k\leq 5; ak=32t12a_k=3\cdot 2^{t-1}-2 for k=2t6k=2t\geq 6; and ak=2t+12a_k=2^{t+1}-2 for k=2t+17k=2t+1\geq 7. We show that sat(n,K2Pk)=2n3+sat(n2,Pk)sat(n, K_{2}\vee P_{k})=2n-3+sat(n-2,P_{k}) for nak+2n\geq a_k+2 and k3k\geq 3, characterize the K2PkK_{2}\vee P_{k}-saturated graphs with sat(n,K2Pk)sat(n,K_{2}\vee P_{k}) edges, the K1PkK_{1}\vee P_{k}-saturated graphs with sat(n,K1Pk)sat(n,K_{1}\vee P_{k}) edges for 3k53\leq k\leq5 and the PkP_{k}-saturated graphs with sat(n,Pk)sat(n, P_{k}) edges for 3k43\leq k\leq4. Furthermore, we propose some questions for further research.

Keywords

Cite

@article{arxiv.2511.20213,
  title  = {Saturation numbers of $K_{2}\vee P_{k}$},
  author = {Xiaoxue Zhang and Lihua You and Xinghui Zhao},
  journal= {arXiv preprint arXiv:2511.20213},
  year   = {2025}
}

Comments

35 pages, 1 figure