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陈学刚 《应用数学与计算数学学报》2005,19(2):85-88
图G的绑定数b(G)是指边集合的最少边数,当这个边集合从G中去掉后所 得图的控制数大于G的控制数. Fischermann等人在[3]中给出了两个猜想: (1)如果 G是一个连通的平面图且围长g(G)≥4,则b(G)≤5;(2)如果G是一个连通的平面图且 围长g(G)≥5,则b(G)≤4.设n3表示度为3的顶点个数,r4和r5分别表示长为4和 5的圈的个数.本文,我们证明了如果r4<(5n3)/2 10,则猜想1成立;如果r5<12,则猜 想2成立. 相似文献
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Let G be a simple graph. A subset S V is a dominating set of G, if for any vertex v V – S there exists a vertex u S such that uv E(G). The domination number, denoted by (G), is the minimum cardinality of a dominating set. In this paper we prove that if G is a 4-regular graph with order n, then (G) 4/11 n 相似文献
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具有最大控制数的连通图的刻画 总被引:3,自引:3,他引:0
设G为一个P阶图,γ(G)表示G的控制数.显然γ(G)≤[p/2].本文的目的是刻画达到这个上界的连通图.主要结果:(1)当p为偶数时,γ(G)=p/2当且仅当G≈C4或者G为某连通图的冠;(2)当p为奇数时,γ(G)=(p-1)/2当且仅当G的每棵生成树为定理3.1中所示的两类树之一. 相似文献
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循环着色是普通着色的推广。本文中,我们研究了一类平面图的循环着色问题,并证明了这类平面图是循环色临界的,但不是普通色临界的,同时,我们还研究了循环着色与图G_k~d中的链之间的关系. 相似文献
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循环着色是普通着色的推广.本文中,我们研究了一类平面图-“花图”的循环着色问题,证明了由2r 1个长为2n 1的圈构成的“辐路”长度为m的花图Fr,m,n的循环色数是2 1/(n-m/2),并证明了在这类图中去掉任何一个点或边后,循环色数都严格减少但普通色数不减少,即这类图是循环色临界的但不是普通色临界的.同时,我们还研究了循环着色与图Gkd中的链之间的关系,给出了两个等价的条件. 相似文献
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6连通图中的可收缩边 总被引:4,自引:0,他引:4
Kriesell(2001年)猜想:如果κ连通图中任意两个相邻顶点的度的和至少是2[5κ/4]-1则图中有κ-可收缩边.本文证明每一个收缩临界6连通图中有两个相邻的度为6的顶点,由此推出该猜想对κ=6成立。 相似文献
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On the Characterization of Maximal Planar Graphs with a Given Signed Cycle Domination Number 下载免费PDF全文
Xiao Ming Pi 《数学学报(英文版)》2018,34(5):911-920
Let G =(V, E) be a simple graph. A function f : E → {+1,-1} is called a signed cycle domination function(SCDF) of G if ∑_(e∈E(C))f(e) ≥ 1 for every induced cycle C of G. The signed cycle domination number of G is defined as γ'_(sc)(G) = min{∑_(e∈E)f(e)| f is an SCDF of G}. This paper will characterize all maximal planar graphs G with order n ≥ 6 and γ'_(sc)(G) = n. 相似文献
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A set S of vertices of a connected graph G is a doubly connected dominating set if every vertex not in S is adjacent to some vertex in S and the subgraphs induced by S and V−S are connected. The doubly connected domination numberγcc(G) is the minimum size of such a set. We prove that when G and are both connected of order n, and we describe the two infinite families of extremal graphs achieving the bound. 相似文献
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1.IntroductionInthispaper,weonlydiscusssimplegraph(withneithermulti-edgenorloop).TheterminologiesnotexplainedcanbeseeninII].Thecyclerankofagraphistheminimumnumberofedgesthatmustberemovedinordertoeliminateallofthecyclesinthegraph.IfGhaspvenices,qedges... 相似文献
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We consider a variant of the Cops and Robber game, in which the robber has unbounded speed, that is, can take any path from her vertex in her turn, but she is not allowed to pass through a vertex occupied by a cop. Let denote the number of cops needed to capture the robber in a graph G in this variant, and let denote the treewidth of G. We show that if G is planar then , and there is a polynomial‐time constant‐factor approximation algorithm for computing . We also determine, up to constant factors, the value of of the Erd?s–Rényi random graph for all admissible values of p, and show that when the average degree is ω(1), is typically asymptotic to the domination number. 相似文献
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In this note more short proofs are given for Faudree-Schelp theorem and Ore theorem. 相似文献
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树的罗马控制数和控制数 总被引:1,自引:0,他引:1
A Roman dominating function on a graph G = (V, E) is a function f : V→{0, 1, 2} satisfying the condition that every vertex u for which f(u) = 0 is adjacent to at least one vertex v for which f(v) - 2. The weight of a Roman dominating function is the value (?). The minimum weight of a Roman dominating function on a graph G, denoted byγR(G), is called the Roman dominating number of G. In this paper, we will characterize a tree T withγR(T) =γ(T) 3. 相似文献
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An acyclic edge coloring of a graph G is a proper edge coloring such that there are no bichromatic cycles.The acyclic edge chromatic number of a graph G is the minimum number k such that there exists an acyclic edge coloring using k colors and is denoted by χ’ a(G).In this paper we prove that χ ’ a(G) ≤(G) + 5 for planar graphs G without adjacent triangles. 相似文献
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An acyclic edge coloring of a graph is a proper edge coloring such that there are no bichromatic cycles. The acyclic chromatic index of a graph is the minimum number k such that there is an acyclic edge coloring using k colors and is denoted by a′(G). It was conjectured by Alon, Sudakov and Zaks (and much earlier by Fiamcik) that a′(G) ? Δ + 2, where Δ = Δ(G) denotes the maximum degree of the graph. If every induced subgraph H of G satisfies the condition |E(H)| ? 2|V(H)|?1, we say that the graph G satisfies Property A. In this article, we prove that if G satisfies Property A, then a′(G) ? Δ + 3. Triangle‐free planar graphs satisfy Property A. We infer that a′(G) ? Δ + 3, if G is a triangle‐free planar graph. Another class of graph which satisfies Property A is 2‐fold graphs (union of two forests). © 2011 Wiley Periodicals, Inc. J Graph Theory 相似文献