围长不小于6且最大度至少为8的平面图的无圈列表边染色

对图G的一个正常边染色,如果图G的任何一个圈至少染三种颜色,则称这个染色为无圈边染色.若L为图G的一个边列表,对图G的一个无圈边染色φ,如果对任意e∈E(G)都有ф(e)∈L(e),则称ф为无圈L-边染色.用a′_(list)(G)表示图G的无圈列表边色数.证明若图G是一个平面图,且它的最大度△≥8,围长g(G)≥6,则a′_(list)(G)=△.     

不含4-,6-圈和相交三角形的平面图的无圈边色数

图G的一个边染色φ:E(G)→{1,2,…,k},若满足任意相邻边都染不同的颜色,且图G不存在双色圈,则称φ为图G的一个无圈k-边染色.图G的无圈边色数χ’_α(G)为使得图G有一个无圈k-边染色的最小正整数k.本文主要证明了对于无4-,6-圈且3-圈与3-圈不相交的平面图G,若Δ(G)≥9,则χ’_α(G)≤Δ(G)+1.     

图 P2×Cn的均匀邻强边色数

对图G(V,E),一正常边染色f若满足(1)对(V)uv∈E(G),f[u]≠f[v],其中f[u]={f(uv)|uv∈E};(2)对任意i≠j,有||E|-|Ej||≤1,其中Ei={e| e∈E(G)且f(e)=i}.则称f为G(V,E)的一k-均匀邻强边染色,简称k-EASC,并且称Xcas(G)=min{k|存在G(V,E)的一k-EASC为G(V,E)的均匀邻强边色数.本文得到了图P2×Cn的均匀邻强边色数.     

图的k符号边控制数

设G=(V,E)是一个图,一个函数f:E→{-1,+1},如果对于G中至少k条边e有sum from e'∈N[e]f(e')≥1成立,则称f为图G的一个k符号边控制函数.一个图的k符号边控制数定义为γ_(ks)^/(G)=min{∑_(e∈E(G))f(e)|f为图G的一个k符号边控制函数}.主要给出了一个图G的k符号边控制数γ_(ks)/(G)=min{∑_(e∈E(G))f(e)|f为图G的一个k符号边控制函数}.主要给出了一个图G的k符号边控制数γ_(ks)^/(G)的若干新下限,并确定了路和圈的k符号边控制数.     

Halin图的邻和可区别边染色与边权点染色

记[k]={1,2,…,k),称为颜色集.设φ:E(G)→[k]为图G的边集合到[k]的映射,令f(v)表示与顶点v关联的边的颜色的加和.如果对任意一条边uv∈E(G),都有φ(u)≠φ(v),f(u)≠f(v),则称φ为图G的邻和可区别[k]-边染色,k的最小值称为图G的邻和可区别边色数,记为ndi_Σ(G).若对任意一条边uv∈E(G),都有f(u)≠f(v),则称φ为图G的k-边权点染色,称图G是k-边权可染的.运用组合零点定理证明了对于最大度不等于4的Halin图有:ndi_∑(G)≤Δ(G)+2,并证明了任一Halin图是4-边权可染的.     

最大度不小于5的外平面图的邻强边染色

图G(V,E)的一k-正常边染色叫做k-邻强边染色当且仅当对任意uv∈E(G)有,f[u]≠f[v],其中f[u]={f(uw)|uw∈E(G)},f(uw)表示边uw的染色.并且x'as(G)=min{k|存在k-图G的邻强边染色}叫做图G的图的邻强边色数.本文证明了对最大度不小于5的外平面图有△≤x'as(G)≤△ 1,且x'as(G)=△ 1当且仅当存在相邻的最大度点.     

Halin-图的邻强边染色

图G(V,E)的正常κ-边染色f叫做图G(V,E)的κ-邻强边染色当且仅当任意uv∈E(G)满足f[u]≠f[v],其中,f[u]={f(uw)|uw∈E(G)},称f是G的κ-临强边染色,简记为κ-ASEC.并且x′_as(G)=min{k|κ-ASEC of G}叫做G(V,E)的邻强边色数.本文研究了△(G)≥5的Halin-图的邻强边色数.     

△(G)=4的Halin-图的邻强边染色

图G(V,E)的一正常k-边染色f称为G(V,E)的一k-邻强边染色(简称k-ASEC)当且仅当任意uv∈E(G)满足f[u]≠f[v],其中f[u]={f(uw)|uw∈E(G)},并称Xas(G)=min{k|存在G的一k-ASEC}为G的邻强边色数.本文研究了△(G)=4的Halin-图的邻强边染色,得到了如下结果对△(G)=4的Halin-图有△(G)=4≤Xas(G)≤△(G)+1=5.     

几类有趣图的奇优美性和奇强协调性

对于简单图G=〈V,E〉,如果存在一个映射f:V(G)→{0,1,2,…,2|E|-1}满足:1)对任意的u,v∈V,若u≠v,则f(u)≠f(v);2)max{f(v)|v∈V}=2|E|-1;3)对任意的e_1,e_2∈E,若e_1≠e_2,则g(e_1)≠g(e_2),此处g(e)=|f(u)+f(v)|,e=uv;4)|g(e)|e∈E}={1,3,5,…,2|E|-1},则称G为奇优美图,f称为G的奇优美标号.设G=〈V,E〉是一个无向简单图.如果存在一个映射f:V(G)→{0,1,2,…,2|E|-1},满足:1)f是单射;2)■uv∈E(G),令f(uv)=f(u)+f(v),有{f(uv)|uv∈E(G)}={1,3,5,…,2|E|-1},则称G是奇强协调图,f称为G的.奇强协调标号或奇强协调值.给出了链图、升降梯等几类有趣图的奇优美标号和奇强协调标号.     

Pm×Kn的邻点可区别全色数

设G是简单图．设f是一个从V(G)∪E(G)到{1,2,…,k}的映射．对每个v∈V(G),令C_f(v)={f(v)}∪{f(vw)|w∈V(G),vw∈E(G)}．如果f是k-正常全染色,且对任意u,v∈V(G),uv∈E(G),有C_f(u)≠C_f(v),那么称f为图G的邻点可区别全染色(简称为k-AVDTC)．数x_(at)(G)=min{k|G有k-AVDTC}称为图G的邻点可区别全色数．本文给出路P_m和完全图K_n的Cartesion积的邻点可区别全色数．     

Equitable list coloring and treewidth

Given lists of available colors assigned to the vertices of a graph G, a list coloring is a proper coloring of G such that the color on each vertex is chosen from its list. If the lists all have size k, then a list coloring is equitable if each color appears on at most ?|V(G)|/k? vertices. A graph is equitably k ‐choosable if such a coloring exists whenever the lists all have size k. Kostochka, Pelsmajer, and West introduced this notion and conjectured that G is equitably k‐choosable for k>Δ(G). We prove this for graphs of treewidth w≤5 if also k≥3w?1. We also show that if G has treewidth w≥5, then G is equitably k‐choosable for k≥max{Δ(G)+w?4, 3w?1}. As a corollary, if G is chordal, then G is equitably k‐choosable for k≥3Δ(G)?4 when Δ(G)>2. © 2009 Wiley Periodicals, Inc. J Graph Theory     

On defected colourings of graphs

Abstract A k-edge-coloring f of a connected graph G is a （A1, A2, , A）-defected k-edge-coloring if there is a smallest integer/ with 1 _ /3 _〈 k - i such that the multiplicity of each color j E {1,2,... ,/3} appearing at a vertex is equal to Aj _〉 2, and each color of {/3 -}- 1,/3 - 2, - , k} appears at some vertices at most one time. The （A1, A2,, A/）-defected chromatic index of G, denoted as X （A1, A2,, A/; G）, is the smallest number such that every （A1,A2,-.., A/）-defected t-edge-coloring of G holds t _〉 X（A1, A2 A;; G）. We obtain A（G） X（A1, ）2, , A/; G） ＋ -- （Ai - 1） _〈 /k（G） 1, and introduce two new chromatic indices of G i=1 as： the vertex pan-biuniform chromatic index X pb （G）, and the neighbour vertex pan-biuniform chromatic index Xnpb（G）, and furthermore find the structure of a tree T having X pb （T） =1.     

The Adaptable Chromatic Number and the Chromatic Number

We prove that the adaptable chromatic number of a graph is at least asymptotic to the square root of the chromatic number. This is best possible.     

Coloring graphs from lists with bounded size of their union

A graph G is k‐choosable if its vertices can be colored from any lists L(ν) of colors with |L(ν)| ≥ k for all ν ∈ V(G). A graph G is said to be (k,?)‐choosable if its vertices can be colored from any lists L(ν) with |L(ν)| ≥k, for all ν∈ V(G), and with . For each 3 ≤ k ≤ ?, we construct a graph G that is (k,?)‐choosable but not (k,? + 1)‐choosable. On the other hand, it is proven that each (k,2k ? 1)‐choosable graph G is O(k · ln k · 2^4k)‐choosable. © 2005 Wiley Periodicals, Inc. J Graph Theory     

The adaptable choosability number grows with the choosability number

The adaptable choosability number of a multigraph G, denoted ch_a(G), is the smallest integer k such that every edge labeling of G and assignment of lists of size k to the vertices of G permits a list coloring of G in which no edge e=uv has both u and v colored with the label of e. We show that ch_a grows with ch, i.e. there is a function f tending to infinity such that ch_a(G)≥f(ch(G)).     

Rainbows in the Hypercube

Let Q_n be a hypercube of dimension n, that is, a graph whose vertices are binary n-tuples and two vertices are adjacent iff the corresponding n-tuples differ in exactly one position. An edge coloring of a graph H is called rainbow if no two edges of H have the same color. Let f(G,H) be the largest number of colors such that there exists an edge coloring of G with f(G,H) colors such that no subgraph isomorphic to H is rainbow. In this paper we start the investigation of this anti-Ramsey problem by providing bounds on f(Q_n,Q_k) which are asymptotically tight for k = 2 and by giving some exact results.     

Star Chromatic Index

The star chromatic index of a graph G is the minimum number of colors needed to properly color the edges of the graph so that no path or cycle of length four is bi‐colored. We obtain a near‐linear upper bound in terms of the maximum degree . Our best lower bound on in terms of Δ is valid for complete graphs. We also consider the special case of cubic graphs, for which we show that the star chromatic index lies between 4 and 7 and characterize the graphs attaining the lower bound. The proofs involve a variety of notions from other branches of mathematics and may therefore be of certain independent interest.