IS there a normal Pk coloring using r colors for a given graph ? Thisproblem is called the (k,r) path chromatic number problem of graphs. This paperproves that the (2, 2) Path chromatic number problem of graphs with m...IS there a normal Pk coloring using r colors for a given graph ? Thisproblem is called the (k,r) path chromatic number problem of graphs. This paperproves that the (2, 2) Path chromatic number problem of graphs with maximum degree4 is NP-complete.展开更多
In this paper, the choosability of outerplanar graphs, 1 tree and strong 1 outerplanar graphs have been described completely. A precise upper bound of the list chromatic number of 1 outerplanar graphs is given, and th...In this paper, the choosability of outerplanar graphs, 1 tree and strong 1 outerplanar graphs have been described completely. A precise upper bound of the list chromatic number of 1 outerplanar graphs is given, and that every 1 outerplanar graph with girth at least 4 is 3 choosable is proved.展开更多
For any vertex u ? V(G), let T N (u) = {u} ∪ {uυ|uυ ? E(G), υ ? υ(G)} ∪ {υ ? υ(G)|uυ ? E(G) and let f be a total k-coloring of G. The total-color neighbor of a vertex u of G is the color set C f(u) = {f(x) | ...For any vertex u ? V(G), let T N (u) = {u} ∪ {uυ|uυ ? E(G), υ ? υ(G)} ∪ {υ ? υ(G)|uυ ? E(G) and let f be a total k-coloring of G. The total-color neighbor of a vertex u of G is the color set C f(u) = {f(x) | x ? T N (u)}. For any two adjacent vertices x and y of V(G) such that C f(x) ≠ C f(y), we refer to f as a k-avsdt-coloring of G (“avsdt” is the abbreviation of “ adjacent-vertex-strongly-distinguishing total”). The avsdt-coloring number of G, denoted by χast(G), is the minimal number of colors required for a avsdt-coloring of G. In this paper, the avsdt-coloring numbers on some familiar graphs are studied, such as paths, cycles, complete graphs, complete bipartite graphs and so on. We prove Δ(G) + 1 ? χast(G) ? Δ(G) + 2 for any tree or unique cycle graph G.展开更多
A proper edge coloring of a graph G is called acyclic if there is no 2-colored cycle in G. The acyclic edge chromatic number of G, denoted by a (G), is the least number of colors in an acyclic edge coloring of G. Alon...A proper edge coloring of a graph G is called acyclic if there is no 2-colored cycle in G. The acyclic edge chromatic number of G, denoted by a (G), is the least number of colors in an acyclic edge coloring of G. Alon et al. conjectured that a (G) Δ(G) + 2 for any graphs. For planar graphs G with girth g(G), we prove that a (G) max{2Δ(G) + 2, Δ(G) + 22} if g(G) 3, a (G) Δ(G) + 2 if g(G) 5, a (G) Δ(G) + 1 if g(G) 7, and a (G) = Δ(G) if g(G) 16 and Δ(G) 3. For series-parallel graphs G, we have a (G) Δ(G) + 1.展开更多
It is conjectured that X as ′ (G) = X t (G) for every k-regular graph G with no C 5 component (k ? 2). This conjecture is shown to be true for many classes of graphs, including: graphs of type 1; 2-regular, 3-regular...It is conjectured that X as ′ (G) = X t (G) for every k-regular graph G with no C 5 component (k ? 2). This conjecture is shown to be true for many classes of graphs, including: graphs of type 1; 2-regular, 3-regular and (|V(G)| - 2)-regular graphs; bipartite graphs; balanced complete multipartite graphs; k-cubes; and joins of two matchings or cycles.展开更多
A proper vertex coloring of a graph G is linear if the graph induced by the vertices of any two color classes is the union of vertex-disjoint paths. The linear chromatic number lc(G) of the graph G is the smallest num...A proper vertex coloring of a graph G is linear if the graph induced by the vertices of any two color classes is the union of vertex-disjoint paths. The linear chromatic number lc(G) of the graph G is the smallest number of colors in a linear coloring of G.In this paper, we prove that every graph G with girth g(G) and maximum degree Δ(G) that can be embedded in a surface of nonnegative characteristic has $ lc(G) = \left\lceil {\frac{{\Delta (G)}} {2}} \right\rceil + 1 $ if there is a pair (Δ, g) ∈ {(13, 7), (9, 8), (7, 9), (5, 10), (3, 13)} such that G satisfies Δ(G) ? Δ and g(G) ? g.展开更多
A proper vertex coloring of a graph G is acyclic if G contains no bicolored cycles.Given a list assignment L={L(v)|v∈V}of G,we say that G is acyclically L-colorable if there exists a proper acyclic coloringπof G suc...A proper vertex coloring of a graph G is acyclic if G contains no bicolored cycles.Given a list assignment L={L(v)|v∈V}of G,we say that G is acyclically L-colorable if there exists a proper acyclic coloringπof G such thatπ(v)∈L(v)for all v∈V.If G is acyclically L-colorable for any list assignment L with|L(v)|k for all v∈V(G),then G is acyclically k-choosable.In this paper,we prove that every planar graph G is acyclically 6-choosable if G does not contain 4-cycles adjacent to i-cycles for each i∈{3,4,5,6}.This improves the result by Wang and Chen(2009).展开更多
The total chromatic number χT (G) of a graph G is the minimum number of colors needed to color the edges and the vertices of G so that incident or adjacent elements have distinct colors. We show that if G is a regula...The total chromatic number χT (G) of a graph G is the minimum number of colors needed to color the edges and the vertices of G so that incident or adjacent elements have distinct colors. We show that if G is a regular graph and d(G) ? 2 3 |V (G)|+ 23 6 , where d(G) denotes the degree of a vertex in G, then χT (G) ? d(G) + 2.展开更多
文摘IS there a normal Pk coloring using r colors for a given graph ? Thisproblem is called the (k,r) path chromatic number problem of graphs. This paperproves that the (2, 2) Path chromatic number problem of graphs with maximum degree4 is NP-complete.
文摘In this paper, the choosability of outerplanar graphs, 1 tree and strong 1 outerplanar graphs have been described completely. A precise upper bound of the list chromatic number of 1 outerplanar graphs is given, and that every 1 outerplanar graph with girth at least 4 is 3 choosable is proved.
基金the National Natural Science Foundation of China (Grant Nos. 10771091, 10661007)
文摘For any vertex u ? V(G), let T N (u) = {u} ∪ {uυ|uυ ? E(G), υ ? υ(G)} ∪ {υ ? υ(G)|uυ ? E(G) and let f be a total k-coloring of G. The total-color neighbor of a vertex u of G is the color set C f(u) = {f(x) | x ? T N (u)}. For any two adjacent vertices x and y of V(G) such that C f(x) ≠ C f(y), we refer to f as a k-avsdt-coloring of G (“avsdt” is the abbreviation of “ adjacent-vertex-strongly-distinguishing total”). The avsdt-coloring number of G, denoted by χast(G), is the minimal number of colors required for a avsdt-coloring of G. In this paper, the avsdt-coloring numbers on some familiar graphs are studied, such as paths, cycles, complete graphs, complete bipartite graphs and so on. We prove Δ(G) + 1 ? χast(G) ? Δ(G) + 2 for any tree or unique cycle graph G.
基金supported by National Natural Science Foundation of China (Grant No. 10871119)NaturalScience Foundation of Shandong Province (Grant No. Y2008A20).
文摘A proper edge coloring of a graph G is called acyclic if there is no 2-colored cycle in G. The acyclic edge chromatic number of G, denoted by a (G), is the least number of colors in an acyclic edge coloring of G. Alon et al. conjectured that a (G) Δ(G) + 2 for any graphs. For planar graphs G with girth g(G), we prove that a (G) max{2Δ(G) + 2, Δ(G) + 22} if g(G) 3, a (G) Δ(G) + 2 if g(G) 5, a (G) Δ(G) + 1 if g(G) 7, and a (G) = Δ(G) if g(G) 16 and Δ(G) 3. For series-parallel graphs G, we have a (G) Δ(G) + 1.
基金supported by National Natural Science Foundation of China (Grant No. 10771091)
文摘It is conjectured that X as ′ (G) = X t (G) for every k-regular graph G with no C 5 component (k ? 2). This conjecture is shown to be true for many classes of graphs, including: graphs of type 1; 2-regular, 3-regular and (|V(G)| - 2)-regular graphs; bipartite graphs; balanced complete multipartite graphs; k-cubes; and joins of two matchings or cycles.
基金supported by National Natural Science Foundation of China (Grant No. 10771197)the Natural Science Foundation of Zhejiang Province of China (Grant No. Y607467)
文摘A proper vertex coloring of a graph G is linear if the graph induced by the vertices of any two color classes is the union of vertex-disjoint paths. The linear chromatic number lc(G) of the graph G is the smallest number of colors in a linear coloring of G.In this paper, we prove that every graph G with girth g(G) and maximum degree Δ(G) that can be embedded in a surface of nonnegative characteristic has $ lc(G) = \left\lceil {\frac{{\Delta (G)}} {2}} \right\rceil + 1 $ if there is a pair (Δ, g) ∈ {(13, 7), (9, 8), (7, 9), (5, 10), (3, 13)} such that G satisfies Δ(G) ? Δ and g(G) ? g.
基金supported by National Natural Science Foundation of China (Grant Nos. 11071223 and 11101377)Natural Science Foundation of Zhejiang Province,China (Gran No. Z6090150)+1 种基金Zhejiang Innovation Project (Grant No. T200905)Zhejiang Normal University Innovation Team Program
文摘A proper vertex coloring of a graph G is acyclic if G contains no bicolored cycles.Given a list assignment L={L(v)|v∈V}of G,we say that G is acyclically L-colorable if there exists a proper acyclic coloringπof G such thatπ(v)∈L(v)for all v∈V.If G is acyclically L-colorable for any list assignment L with|L(v)|k for all v∈V(G),then G is acyclically k-choosable.In this paper,we prove that every planar graph G is acyclically 6-choosable if G does not contain 4-cycles adjacent to i-cycles for each i∈{3,4,5,6}.This improves the result by Wang and Chen(2009).
基金supported by the Natural Science Foundation of Chongqing Science and Technology Commission(Grant No. 2007BB2123)
文摘The total chromatic number χT (G) of a graph G is the minimum number of colors needed to color the edges and the vertices of G so that incident or adjacent elements have distinct colors. We show that if G is a regular graph and d(G) ? 2 3 |V (G)|+ 23 6 , where d(G) denotes the degree of a vertex in G, then χT (G) ? d(G) + 2.
