Tangles, trees, and flowers
نویسندگان
چکیده
منابع مشابه
Paths, Trees, and Flowers
“Jack Edmonds has been one of the creators of the field of combinatorial optimization and polyhedral combinatorics. His 1965 paper ‘Paths, Trees, and Flowers’ [1] was one of the first papers to suggest the possibility of establishing a mathematical theory of efficient combinatorial algorithms . . . ” [from the award citation of the 1985 John von Neumann Theory Prize, awarded annually since 1975...
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An asteroidal triple is a set of three independent vertices in a graph such that any two vertices in the set are connected by a path which avoids the neighbourhood of the third. A classical result by Lekkerkerker and Boland [10] showed that interval graphs are precisely the chordal graphs that do not have asteroidal triples. Interval graphs are chordal, as are the directed path graphs and the p...
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A simple graph G = (V,E) admits an H-covering if every edge in E is contained in a subgraph H ′ = (V , E) of G which is isomorphic to H . In this case we say that G is H-supermagic if there is a bijection f : V ∪ E → {1, . . . |V | + |E|} such that f(V ) = {1, . . . , |V |} and ∑ v∈V (H) f(v) + ∑ e∈E(H) f(e) is constant over all subgraphs H ′ of G which are isomorphic to H . In this paper, we s...
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Floral color changes and retention of old flowers are frequently combined phenomena restricted to the floral guide or single flowers in few-flowered inflorescences. They are thought to increase the attractiveness over long distances and to direct nearby pollinators toward the rewarding flowers. In Tibouchina pulchra, a massively flowering tree, the whole flower changes its color during anthesis...
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We start with some terminology from differential topology [1]. Let be a circle and ≥ 2 be an integer. An immersion : → R is a smooth function whose derivative never vanishes. An embedding : → R is an immersion that is oneto-one. It follows that () is a manifold but () need not be ( is only locally one-to-one, so consider the map that twists into a figure eight). A knot is a s...
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ژورنال
عنوان ژورنال: Journal of Combinatorial Theory, Series B
سال: 2013
ISSN: 0095-8956
DOI: 10.1016/j.jctb.2013.03.002