C_n^2图的符号控制数

设图G=G(V,E),令函数f:V→{-1,1},f的权w(f)=∑v∈Vf[v],对v∈V,定义f[v]=∑u∈N[v]f(u),这里N[v]表示V中顶点v及其邻点的集合。图G的符号控制函数为f:V→{-1,1}满足对所有的v∈V有f[v]≥1,图G的符号控制数γs(G)就是图G上符号控制数的最小权,称其f为图G的γs-函数。研究了C2n图,通过给出它的一个γs-函数得到了其符号控制数。

Bounds on the clique-transversal number of regular graphs

A clique-transversal set D of a graph G is a set of vertices of G such that D meets all cliques of G. The clique-transversal number, denoted τ c (G), is the minimum cardinality of a clique-transversal set in G. In this paper we present the bounds on the clique-transversal number for regular graphs and characterize the extremal graphs achieving the lower bound. Also, we give the sharp bounds on the clique-transversal number for claw-free cubic graphs and we characterize the extremal graphs achieving the lower bound.