设G是有限简单无向图,使G—S每个分支的阶至少为4的边割S称为G的4阶限制边割.G的4阶限制边连通度λ4(G)是G的4阶限制边割之中最少的边数,达到最小的叫λ4边割.定义ξ4(G)=min{ (U):UCV(G),G[U]是4阶连通子图},此处 (U)表示恰好有一个端点在U中的边数.若λ4(G)=ξ4(G),则称G是λ4最优的.若任意λ4边割都孤立一个4阶连通子图,则称G是超级λ4连通的.给出图是λ4最优和超级v4连通的度条件,并举例说明条件的最好可能性.
Let G be a finite, simple and undirected graph. An edge-cut S of G is 4-restricted if each component of G -S contains at least 4 vertices. The 4-restricted edge connectivity of G, denoted as λ4(G), is defined as the minimum cardinality of all 4-restricted edge-cuts, and the minimum ones are called λ4-edge-cuts. Let ξ4 (G) = min{ (U) : UC V(G), G[ U] is a connected subgraph of order 4 of G,where O(U) denotes the edge number exactly having one endvertex in U. A graph is λ4- optimal if λ4-(G) =ξ4 (G). A graph is super-λ4 if every λ4- edge-cut isolates a connected subgraph of order 4. This paper presents degree conditions super-λ4. Moreover, this paper gives some cases possible. for a graph to be λ4- optimal and a graph to be to demonstrate that these conditions are the most possible.