The edge-face chromatic number Xef （G） of a plane graph G is the least number of colors assigned to the edges and faces such that every adjacent or incident pair of them receives different colors. In this article, t...The edge-face chromatic number Xef （G） of a plane graph G is the least number of colors assigned to the edges and faces such that every adjacent or incident pair of them receives different colors. In this article, the authors prove that every 2-connected plane graph G with △（G）≥｜G｜ - 2≥9 has Xef（G） = △（G）.展开更多
Wang Vei-fan proved that the edge-face chromatic number of a 2-connected1-tree with the maximum degree is not less than 6 is its maximum degree, and he conjecturedthat it is true when the maximum degree is 5. This pap...Wang Vei-fan proved that the edge-face chromatic number of a 2-connected1-tree with the maximum degree is not less than 6 is its maximum degree, and he conjecturedthat it is true when the maximum degree is 5. This paper proves the conjecture.展开更多
Definition 1. Assume that G（V, E, F）is a 3-connected plane graph. Remove all edges on the boundary of a face f<sub>0</sub> whose degree of all vertices of $ V（f-0）$ is 3 such that G becomes a tree T wh...Definition 1. Assume that G（V, E, F）is a 3-connected plane graph. Remove all edges on the boundary of a face f<sub>0</sub> whose degree of all vertices of $ V（f-0）$ is 3 such that G becomes a tree T whose degree of all vertices except those of V（f<sub>0</sub>） is at least 3. Then G is called a Halin-graph, f<sub>0</sub>展开更多
For a general graph G, M（G） denotes its Mycielski graph. This article gives a number of new sufficient conditions for G to have the circular chromatic number xc（M（G）） equals to the chromatic number x（M（G））, ...For a general graph G, M（G） denotes its Mycielski graph. This article gives a number of new sufficient conditions for G to have the circular chromatic number xc（M（G）） equals to the chromatic number x（M（G））, which have improved some best sufficient conditions published up to date.展开更多
Let G be an outerplane graph with maximum degree A and the entire chromatic number Xvef（G）. This paper proves that if △ ≥6, then △＋ 1≤Xvef（G）≤△＋ 2, and Xvef （G） = △＋ 1 if and only if G has a matching M...Let G be an outerplane graph with maximum degree A and the entire chromatic number Xvef（G）. This paper proves that if △ ≥6, then △＋ 1≤Xvef（G）≤△＋ 2, and Xvef （G） = △＋ 1 if and only if G has a matching M consisting of some inner edges which covers all its vertices of maximum degree.展开更多
Let x（G^2） denote the chromatic number of the square of a maximal outerplanar graph G and Q denote a maximal outerplanar graph obtained by adding three chords y1 y3, y3y5, y5y1 to a 6-cycle y1y2…y6y1. In this paper...Let x（G^2） denote the chromatic number of the square of a maximal outerplanar graph G and Q denote a maximal outerplanar graph obtained by adding three chords y1 y3, y3y5, y5y1 to a 6-cycle y1y2…y6y1. In this paper, it is proved that △ ＋ 1 ≤ x（G^2） ≤△ ＋ 2, and x（G^2） = A ＋ 2 if and only if G is Q, where A represents the maximum degree of G.展开更多
Let G be a graph and k be a positive integer. We consider a game with two players Alice and Bob who alternate in coloring the vertices of G with a set of k colors. In every turn, one vertex will be chosen by one playe...Let G be a graph and k be a positive integer. We consider a game with two players Alice and Bob who alternate in coloring the vertices of G with a set of k colors. In every turn, one vertex will be chosen by one player. Alice’s goal is to color all vertices with the k colors, while Bob’s goal is to prevent her. The game chromatic number denoted by?χg(G), is the smallest k such that Alice has a winning strategy with k colors. In this paper, we determine the game chromatic number?χg of circulant graphs?Cn(1,2), , and generalized Petersen graphs GP(n,2), GP(n,3).展开更多
An integer distance graph is a graph G(Z,D) with the set of integers as vertex set and an edge joining two vertices u and?v if and only if ∣u - v∣D where D is a subset of the positive integers. It is known that x(G(...An integer distance graph is a graph G(Z,D) with the set of integers as vertex set and an edge joining two vertices u and?v if and only if ∣u - v∣D where D is a subset of the positive integers. It is known that x(G(Z,D) )=4 where P is a set of Prime numbers. So we can allocate the subsets D of P to four classes, accordingly as is 1 or 2 or 3 or 4. In this paper we have considered the open problem of characterizing class three and class four sets when the distance set D is not only a subset of primes P but also a special class of primes like Additive primes, Deletable primes, Wedderburn-Etherington Number primes, Euclid-Mullin sequence primes, Motzkin primes, Catalan primes, Schroder primes, Non-generous primes, Pell primes, Primeval primes, Primes of Binary Quadratic Form, Smarandache-Wellin primes, and Highly Cototient number primes. We also have indicated the membership of a number of special classes of prime numbers in class 2 category.展开更多
An acyclic coloring of a graph is a proper vertex coloring such that the union of any two color classes induces a disjoint collection of trees.The purpose of this paper is to derive exact values of acyclic chromatic n...An acyclic coloring of a graph is a proper vertex coloring such that the union of any two color classes induces a disjoint collection of trees.The purpose of this paper is to derive exact values of acyclic chromatic number of some graphs.展开更多
A set <em>S ⊆ V (G)</em> is called a geodetic set if every vertex of <em>G</em> lies on a shortest <em>u-v</em> path for some <em>u, v ∈ S</em>, the minimum cardinality...A set <em>S ⊆ V (G)</em> is called a geodetic set if every vertex of <em>G</em> lies on a shortest <em>u-v</em> path for some <em>u, v ∈ S</em>, the minimum cardinality among all geodetic sets is called geodetic number and is denoted by <img src="Edit_82259359-0135-4a65-9378-b767f0405b48.png" alt="" />. A set <em>C ⊆ V (G)</em> is called a chromatic set if <em>C</em> contains all vertices of different colors in<em> G</em>, the minimum cardinality among all chromatic sets is called the chromatic number and is denoted by <img src="Edit_d849148d-5778-459b-abbb-ff25b5cd659b.png" alt="" />. A geo-chromatic set<em> S</em><sub><em>c</em></sub><em> ⊆ V (G</em><em>)</em> is both a geodetic set and a chromatic set. The geo-chromatic number <img src="Edit_505e203c-888c-471c-852d-4b9c2dd1a31c.png" alt="" /><em> </em>of<em> G</em> is the minimum cardinality among all geo-chromatic sets of<em> G</em>. In this paper, we determine the geodetic number and the geo-chromatic number of 2-cartesian product of some standard graphs like complete graphs, cycles and paths.展开更多
A proper total-coloring of graph G is said to be?equitable if the number of elements (vertices and edges) in any?two color classes differ by at most one, which the required?minimum number of colors is called the equit...A proper total-coloring of graph G is said to be?equitable if the number of elements (vertices and edges) in any?two color classes differ by at most one, which the required?minimum number of colors is called the equitable total chromatic?number. In this paper, we prove some theorems on equitable?total coloring and derive the equitable total chromatic numbers?of Pm V?Sn, Pm V?Fn and Pm V Wn.展开更多
图 G 的全部的色彩的数字 T (G) 是需要渲染 G 的元素(顶点和边) 的颜色的最小的数字以便不邻近或元素的事件对收到一样的颜色。G 被称为类型 1 如果 T (G)=(G)+ 1。在这份报纸，我们证明完全的由两部组成的图 Km， n 和周期 Cn 的 join...图 G 的全部的色彩的数字 T (G) 是需要渲染 G 的元素(顶点和边) 的颜色的最小的数字以便不邻近或元素的事件对收到一样的颜色。G 被称为类型 1 如果 T (G)=(G)+ 1。在这份报纸，我们证明完全的由两部组成的图 Km， n 和周期 Cn 的 join 具有类型 1。展开更多
Let G be a maximal outerplane graph and X0(G) the complete chromatic number of G. This paper determines exactly X0(G) for △(G)≠5 and proves 6≤X0.(G)≤7 for △(G) = 5, where △(G) is the maximum degree of vertices o...Let G be a maximal outerplane graph and X0(G) the complete chromatic number of G. This paper determines exactly X0(G) for △(G)≠5 and proves 6≤X0.(G)≤7 for △(G) = 5, where △(G) is the maximum degree of vertices of G.展开更多
For a graph G, let be the chromatic number of G. It is well-known that holds for any graph G with clique number . For a hereditary graph class , whether there exists a function f such that holds for every has been wid...For a graph G, let be the chromatic number of G. It is well-known that holds for any graph G with clique number . For a hereditary graph class , whether there exists a function f such that holds for every has been widely studied. Moreover, the form of minimum such an f is also concerned. A result of Schiermeyer shows that every -free graph G with clique number has . Chudnovsky and Sivaraman proved that every -free with clique number graph is -colorable. In this paper, for any -free graph G with clique number , we prove that . The main methods in the proof are set partition and induction.展开更多
A planar graph G is called a i pseudo outerplanar graph if there is a subset V 0V(G),|V 0|=i, such that G-V 0 is an outerplanar graph. In particular, when G-V 0 is a forest, G is called a i...A planar graph G is called a i pseudo outerplanar graph if there is a subset V 0V(G),|V 0|=i, such that G-V 0 is an outerplanar graph. In particular, when G-V 0 is a forest, G is called a i pseudo tree. In this paper, the following results are proved: (i) The conjecture on the total coloring is true for all 1 pseudo outerplanar graphs; (ii) χ t(G)=Δ(G)+1 for any 1 pseudo outerplanar graph G with Δ(G)6 and for any 1 pseudo tree G with Δ(G)3, where χ t(G) is the total chromatic number of a graph G .展开更多
Melnikov(1975) conjectured that the edges and faces of a plane graph G can be colored with △(G) + 3 colors so that any two adjacent or incident elements receive distinct colors, where △(G) denotes the maximum degree...Melnikov(1975) conjectured that the edges and faces of a plane graph G can be colored with △(G) + 3 colors so that any two adjacent or incident elements receive distinct colors, where △(G) denotes the maximum degree of G. This paper proves the conjecture for the case △(G) ≤4.展开更多
基金This research is supported by NNSF of China(40301037, 10471131)
文摘The edge-face chromatic number Xef （G） of a plane graph G is the least number of colors assigned to the edges and faces such that every adjacent or incident pair of them receives different colors. In this article, the authors prove that every 2-connected plane graph G with △（G）≥｜G｜ - 2≥9 has Xef（G） = △（G）.
文摘Wang Vei-fan proved that the edge-face chromatic number of a 2-connected1-tree with the maximum degree is not less than 6 is its maximum degree, and he conjecturedthat it is true when the maximum degree is 5. This paper proves the conjecture.
文摘Definition 1. Assume that G（V, E, F）is a 3-connected plane graph. Remove all edges on the boundary of a face f<sub>0</sub> whose degree of all vertices of $ V（f-0）$ is 3 such that G becomes a tree T whose degree of all vertices except those of V（f<sub>0</sub>） is at least 3. Then G is called a Halin-graph, f<sub>0</sub>
基金Supported by National Science Foundation of China (10371048)the Science Foundation of Three Gorges University.
文摘For a general graph G, M（G） denotes its Mycielski graph. This article gives a number of new sufficient conditions for G to have the circular chromatic number xc（M（G）） equals to the chromatic number x（M（G））, which have improved some best sufficient conditions published up to date.
文摘Let G be an outerplane graph with maximum degree A and the entire chromatic number Xvef（G）. This paper proves that if △ ≥6, then △＋ 1≤Xvef（G）≤△＋ 2, and Xvef （G） = △＋ 1 if and only if G has a matching M consisting of some inner edges which covers all its vertices of maximum degree.
文摘Let x（G^2） denote the chromatic number of the square of a maximal outerplanar graph G and Q denote a maximal outerplanar graph obtained by adding three chords y1 y3, y3y5, y5y1 to a 6-cycle y1y2…y6y1. In this paper, it is proved that △ ＋ 1 ≤ x（G^2） ≤△ ＋ 2, and x（G^2） = A ＋ 2 if and only if G is Q, where A represents the maximum degree of G.
文摘Let G be a graph and k be a positive integer. We consider a game with two players Alice and Bob who alternate in coloring the vertices of G with a set of k colors. In every turn, one vertex will be chosen by one player. Alice’s goal is to color all vertices with the k colors, while Bob’s goal is to prevent her. The game chromatic number denoted by?χg(G), is the smallest k such that Alice has a winning strategy with k colors. In this paper, we determine the game chromatic number?χg of circulant graphs?Cn(1,2), , and generalized Petersen graphs GP(n,2), GP(n,3).
文摘An integer distance graph is a graph G(Z,D) with the set of integers as vertex set and an edge joining two vertices u and?v if and only if ∣u - v∣D where D is a subset of the positive integers. It is known that x(G(Z,D) )=4 where P is a set of Prime numbers. So we can allocate the subsets D of P to four classes, accordingly as is 1 or 2 or 3 or 4. In this paper we have considered the open problem of characterizing class three and class four sets when the distance set D is not only a subset of primes P but also a special class of primes like Additive primes, Deletable primes, Wedderburn-Etherington Number primes, Euclid-Mullin sequence primes, Motzkin primes, Catalan primes, Schroder primes, Non-generous primes, Pell primes, Primeval primes, Primes of Binary Quadratic Form, Smarandache-Wellin primes, and Highly Cototient number primes. We also have indicated the membership of a number of special classes of prime numbers in class 2 category.
文摘An acyclic coloring of a graph is a proper vertex coloring such that the union of any two color classes induces a disjoint collection of trees.The purpose of this paper is to derive exact values of acyclic chromatic number of some graphs.
文摘A set <em>S ⊆ V (G)</em> is called a geodetic set if every vertex of <em>G</em> lies on a shortest <em>u-v</em> path for some <em>u, v ∈ S</em>, the minimum cardinality among all geodetic sets is called geodetic number and is denoted by <img src="Edit_82259359-0135-4a65-9378-b767f0405b48.png" alt="" />. A set <em>C ⊆ V (G)</em> is called a chromatic set if <em>C</em> contains all vertices of different colors in<em> G</em>, the minimum cardinality among all chromatic sets is called the chromatic number and is denoted by <img src="Edit_d849148d-5778-459b-abbb-ff25b5cd659b.png" alt="" />. A geo-chromatic set<em> S</em><sub><em>c</em></sub><em> ⊆ V (G</em><em>)</em> is both a geodetic set and a chromatic set. The geo-chromatic number <img src="Edit_505e203c-888c-471c-852d-4b9c2dd1a31c.png" alt="" /><em> </em>of<em> G</em> is the minimum cardinality among all geo-chromatic sets of<em> G</em>. In this paper, we determine the geodetic number and the geo-chromatic number of 2-cartesian product of some standard graphs like complete graphs, cycles and paths.
文摘A proper total-coloring of graph G is said to be?equitable if the number of elements (vertices and edges) in any?two color classes differ by at most one, which the required?minimum number of colors is called the equitable total chromatic?number. In this paper, we prove some theorems on equitable?total coloring and derive the equitable total chromatic numbers?of Pm V?Sn, Pm V?Fn and Pm V Wn.
基金Project supported by the Vatural SCience Foundation of LNEC.
文摘Let G be a maximal outerplane graph and X0(G) the complete chromatic number of G. This paper determines exactly X0(G) for △(G)≠5 and proves 6≤X0.(G)≤7 for △(G) = 5, where △(G) is the maximum degree of vertices of G.
文摘For a graph G, let be the chromatic number of G. It is well-known that holds for any graph G with clique number . For a hereditary graph class , whether there exists a function f such that holds for every has been widely studied. Moreover, the form of minimum such an f is also concerned. A result of Schiermeyer shows that every -free graph G with clique number has . Chudnovsky and Sivaraman proved that every -free with clique number graph is -colorable. In this paper, for any -free graph G with clique number , we prove that . The main methods in the proof are set partition and induction.
文摘A planar graph G is called a i pseudo outerplanar graph if there is a subset V 0V(G),|V 0|=i, such that G-V 0 is an outerplanar graph. In particular, when G-V 0 is a forest, G is called a i pseudo tree. In this paper, the following results are proved: (i) The conjecture on the total coloring is true for all 1 pseudo outerplanar graphs; (ii) χ t(G)=Δ(G)+1 for any 1 pseudo outerplanar graph G with Δ(G)6 and for any 1 pseudo tree G with Δ(G)3, where χ t(G) is the total chromatic number of a graph G .
文摘Melnikov(1975) conjectured that the edges and faces of a plane graph G can be colored with △(G) + 3 colors so that any two adjacent or incident elements receive distinct colors, where △(G) denotes the maximum degree of G. This paper proves the conjecture for the case △(G) ≤4.
