171 research outputs found
Choosability of a weighted path and free-choosability of a cycle
A graph with a list of colors and weight for each vertex
is -colorable if one can choose a subset of colors from
for each vertex , such that adjacent vertices receive disjoint color
sets. In this paper, we give necessary and sufficient conditions for a weighted
path to be -colorable for some list assignments . Furthermore, we
solve the problem of the free-choosability of a cycle.Comment: 9 page
Extended core and choosability of a graph
A graph is -choosable if for any color list of size associated
with each vertices, one can choose a subset of colors such that adjacent
vertices are colored with disjoint color sets. This paper shows an equivalence
between the -choosability of a graph and the -choosability of one
of its subgraphs called the extended core. As an application, this result
allows to prove the -choosability and -colorability of
triangle-free induced subgraphs of the triangular lattice.Comment: 10 page
Total weight choosability in Hypergraphs
A total weighting of the vertices and edges of a hypergraph is called
vertex-coloring if the total weights of the vertices yield a proper coloring of
the graph, i.e., every edge contains at least two vertices with different
weighted degrees. In this note we show that such a weighting is possible if
every vertex has two, and every edge has three weights to choose from,
extending a recent result on graphs to hypergraphs
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