منابع مشابه
Mixed Interval Hypergraphs
We investigate the coloring properties of mixed interval hypergraphs having two families of subsets: the edges and the co-edges. In every edge at least two vertices have different colors. The notion of a co-edge was introduced recently in [2,3]: in every such a subset at least two vertices have the same color. The upper (lower) chromatic number is defined as a maximum (minimum) number of colors...
متن کاملThe mixed hypergraphs
We introduce the notion of an anti-edge of a hypergraph, which is a non-overall polychromatic subset of vertices. The maximal number of colors, for which there exists a coloring of a hy-pergraph using all colors, is called an upper chromatic number of a hypergraph H and denoted by ¯ χ(H). The general algorithm for computing the numbers of all colorings of mixed (containing edge and anti-edge se...
متن کاملOn Planar Mixed Hypergraphs
A mixed hypergraph H is a triple (V, C,D) where V is its vertex set and C and D are families of subsets of V , C–edges and D–edges. A mixed hypergraph is a bihypergraph iff C = D. A hypergraph is planar if its bipartite incidence graph is planar. A vertex coloring of H is proper if each C–edge contains two vertices with the same color and each D–edge contains two vertices with different colors....
متن کاملColouring Planar Mixed Hypergraphs
A mixed hypergraph is a tripleH = (V, C,D) where V is the vertex set and C and D are families of subsets of V , the C-edges and D-edges, respectively. A k-colouring of H is a mapping c : V → [k] such that each C-edge has at least two vertices with a Common colour and each D-edge has at least two vertices of Different colours. H is called a planar mixed hypergraph if its bipartite representation...
متن کاملUncolorable Mixed Hypergraphs
A mixed hypergraph H = (X; A; E) consists of the vertex set X and two families of subsets: the family E of edges and the family A of co-edges. In a coloring every edge E 2 E has at least two vertices of diierent colors, while every co-edge A 2 A has at least two vertices of the same color. The largest (smallest) number of colors for which there exists a coloring of a mixed hypergraph H using al...
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ژورنال
عنوان ژورنال: Discrete Applied Mathematics
سال: 1997
ISSN: 0166-218X
DOI: 10.1016/s0166-218x(97)89209-8