图的广义连通度的概念是由Chartrand等人引入的.令S表示图G的一个非空顶点集,k(S)表示图G中连结S的内部不交树的最大数目.那么,对任意一个满足2≤r≤n的整数r,定义G的广义r-连通度为所有K(S)中的最小值,其中S取遍G的顶点集合的r-元子集.显然,K2(G)=K(G),即为图G的顶点连通度.所以广义连通度是经典连通度的一个自然推广.本文研究了随机图的广义3-连通度,证明了对任一给定的整数k,k≥1,p=10gn+(k+1)loglogn-loglogn/n是关于性质K3(G(扎,p))≥k的紧阈值函数.我们得到的结果可以看作是Bollobas和Thomason给出的关于经典连通度结果的推广.
The generalized connectivity of a graph G was introduced by Chartrand et al. Let S be a nonempty set of vertices of G, and k(S) denote the largest number of internally disjoint trees connecting S in G. Then for an integer r with 2 〈 r 〈 n, the generalized r-connectivity kr(G) of G is the minimum k(S) where S runs over all the r-subsets of the vertex set of G. Obviously, k2(G) = k(G), is the vertex connectivity of G, and hence the generalized connectivity is a natural generalization of the vertex connectivity. In this paper, we study the generalized 3-connectivity of random graphs and prove that for every fixed integer k ≥ 1,p=10gn+(k+1)loglogn-loglogn/nis a sharp threshold function for the property k3(G(n,p)) ≥ k, which could be seen as a counterpart of Bollobas and Thomason's result for vertex connectivity.