设S是连通图G的一个边割。若G-S不包含孤立点,则称S是G的一个限制边割。如果图G的每个最小限制边割恰好分离出图G的一条边,则称图G是超级限制边连通的,简称超级-λ'的。设G是一个阶n≥4的连通无三角图。本文证明了若G中任意满足dist(u,v)=2的点对u,v∈V(G)有d(u)+d(v)≥2[n+2/4]+3,则G是超级-λ'的。最后,举例说明该结论是最好的。
An edge cut S of a connected graph G is called as a restricted edge cut if G-S contains no isolated vertices. A graph is to be super restricted edge-connected for short super-λ',if every minimum restricted edge cut isolates an edge. In this paper,we study the degree sum conditions for triangle-free graphs to be super restricted edge connectivity,and prove that: Let G be a connected triangle-free graph of order. If d( u) + d( v) ≥2[(n +2)/4]+ 3 for each pair vertices u,v∈V( G) with dist( u,v) = 2,then G is super-λ'. Moreover,the result is demonstrated to be the best possible.