Longest Cycles in 3-Connected, K_(1,3)-Free Graphs

The graph considered in this paper is an undireeted graph of order n,without loops alld multiple edges.Denotea by V(G)the vertex set of graph G,by |V(G)| the cardinality of V(G),by K(G)the connectivity of G,by δ the minimum degree of G.A eyele in G is considered as a Subgraph of G,and for a Subgraph H of G.1et G-H denote the Subgraph of G inducedby vertex set V(G)-y(日).M. M.Marthews and D.P.Summer proved in 1986 that eVery 2-eonneeted, K_1,3-free     

Longest Cycles in 2-Connected Regular Claw-Free Graphs

All graph considered In this paper are undirected and finite,without loops ormultip1e edges.A graph is called claw-free if it does not contain a copy of K_(1,3)as an induced subgraph.For a graph C,let δ(G)denote the minimum degree of G.There have been a great many results in recent years dealing with longest cycles.for example, M.Matthews and D.Summer have shown the following result:     

无$K_{1,4}$子图的图的路覆盖

For a graph G, a path cover is a set of vertex disjoint paths covering all the vertices of G, and a path cover number of G, denoted by p(G), is the minimum number of paths in a path cover among all the path covers of G. In this paper, we prove that if G is a K_(1,4)-free graph of order n and σ_(k+1)(G) ≥ n-k, then p(G) ≤ k, where σ_(k+1)(G) = min{∑v∈S d(v) : S is an independent set of G with |S| = k + 1}.     

半无爪可迹图的度和条件

可迹图即为一个含有Hamilton路的图.令$N[v]=N(v)\cup\{v\}$, $J(u,v)=\{w\in N(u)\cap N(v):N(w)\subseteq N[u]\cup N[v]\}$.若图中任意距离为2的两点$u,v$满足$J(u,v)\neq \emptyset$,则称该图为半无爪图.令$\sigma_{k}(G)=\min\{\sum_{v\in S}d(v):S$为$G$中含有$k$个点的独立集\},其中$d(v)$表示图$G$中顶点$v$的度.本论文证明了若图$G$为一个阶数为$n$的连通半无爪图,且$\sigma_{3}(G)\geq {n-2}$,则图$G$为可迹图; 文中给出一个图例,说明上述结果中的界是下确界; 此外,我们证明了若图$G$为一个阶数为$n$的连通半无爪图,且$\sigma_{2}(G)\geq \frac{2({n-2})}{3}$,则该图为可迹图.     

无爪图中的最长圈

本文证明了:n阶3—连通无爪图G中的最长圈的长至少为min{4k—5,n},这里k是G的最小度.     

Hamiltonian Cycles in 3-connected Claw-Free Graphs

All graphs considered in this paper are undirected and finite,without loops or mu-Itiple edges. A graph is called claw-free if it does not contain a copy of K_(1,3) as aninduced subgraph. For a subgraph H of G, G-H denotes the induced subgraph of byV(G)-V(H). If K and L are subsets or subgraphs, we denote by N_K(L) the set ofvertices in K which are adjacent to some vertex in L. In recent years there nave beena great many papers dealing with hamiltonian cycles in claw-free graphs. M.M.Matt-