English

The domination number and the least Q-eigenvalue II

Combinatorics 2017-09-05 v2

Abstract

Denote by Lg,lL_{g, l} the lollipoplollipop graphgraph obtained by attaching a pendant path P=vgvg+1vg+l\mathbb{P}=v_{g}v_{g+1}\cdots v_{g+l} (l1l\geq 1) to a cycle C=v1v2vgv1\mathbb{C}=v_{1}v_{2}\cdots v_{g}v_{1} (g3g\geq 3). A Fg,l\mathcal {F}_{g, l}-graphgraph of order ng+1n\geq g+1 is defined to be the graph obtained by attaching ngln-g-l pendent vertices to some of the nonpendant vertices of Lg,lL_{g, l} in which each vertex other than vg+l1v_{g+l-1} is attached at most one pendant vertex. A Fg,l\mathcal {F}^{\circ}_{g, l}-graph is a Fg,l\mathcal {F}_{g, l}-graphgraph in which vgv_{g} is attached with pendant vertex. Denote by qminq_{min} the leastleast QQ-eigenvalueeigenvalue of a graph. In this paper, we proceed on considering the domination number, the least QQ-eigenvalue of a graph as well as their relation. Further results obtained are as follows: (i)\mathrm{(i)} some results about the changing of the domination number under the structural perturbation of a graph are represented; (ii)\mathrm{(ii)} among all nonbipartite unicyclic graphs of order nn, with both domination number γ\gamma and girth gg (gn1g\leq n-1), the minimum qminq_{min} attains at a Fg,l\mathcal {F}_{g, l}-graph for some ll; (iii)\mathrm{(iii)} among the nonbipartite graphs of order nn and with given domination number which contain a Fg,l\mathcal {F}^{\circ}_{g, l}-graph as a subgraph, some lower bounds for qminq_{min} are represented; (iv)\mathrm{(iv)} among the nonbipartite graphs of order nn and with given domination number n2\frac{n}{2}, n12\frac{n-1}{2}, the minimum qminq_{min} is completely determined respectively; (v)\mathrm{(v)} among the nonbipartite graphs of order n4n\geq 4, and with both domination number n+13<γn2\frac{n+1}{3}<\gamma\leq \frac{n}{2} and odd-girth (the length of the shortest odd cycle) at most 55, the minimum qminq_{min} is completely determined.

Keywords

Cite

@article{arxiv.1707.07123,
  title  = {The domination number and the least Q-eigenvalue II},
  author = {Guanglong Yu},
  journal= {arXiv preprint arXiv:1707.07123},
  year   = {2017}
}

Comments

30 pages

R2 v1 2026-06-22T20:54:36.799Z