منابع مشابه
Directed triangles in directed graphs
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In this paper we initialize the study of independent domination in directed graphs. We show that an independent dominating set of an orientation of a graph is also an independent dominating set of the underlying graph, but that the converse is not true in general. We then prove existence and uniqueness theorems for several classes of digraphs including orientations of complete graphs, paths, tr...
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A particularly interesting special case that is still open is: any digraph on n vertices with minimum outdegree at least n 3 contains a directed triangle. Short of proving this, one may seek a value c as small as possible such that every digraph on n vertices with minimum outdegree at least cn contains a directed triangle. This was the strategy of Caccetta and Ha ggkvist [3], who showed that c ...
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Using a recent result of Chudnovsky, Seymour, and Sullivan, we slightly improve two bounds related to the Caccetta-Haggkvist Conjecture. Namely, we show that if α ≥ 0.35312, then each n-vertex digraph D with minimum outdegree at least αn has a directed 3-cycle. If β ≥ 0.34564, then every n-vertex digraph D in which the outdegree and the indegree of each vertex is at least βn has a directed 3-cy...
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ژورنال
عنوان ژورنال: Discrete Mathematics
سال: 1992
ISSN: 0012-365X
DOI: 10.1016/0012-365x(92)90719-v