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Sökning: L773:0012 365X OR L773:1872 681X > Luleå tekniska universitet

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1.
  • Asratian, Armen, et al. (författare)
  • On the number of nearly perfect matchings in almost regular uniform hypergraphs
  • 1999
  • Ingår i: Discrete Mathematics. - : Elsevier. - 0012-365X .- 1872-681X. ; 207:1, s. 1-8
  • Tidskriftsartikel (refereegranskat)abstract
    • Strengthening the result of R dl and Frankl (Europ. J. Combin 6 (1985) 317-326), Pippenger proved the theorem stating the existence of a nearly perfect matching in almost regular uniform hypergraph satisfying some conditions (see J. Combin. Theory A 51 (1989) 24-42). Grable announced in J. Combin. Designs 4 (4) (1996) 255-273 that such hypergraphs have exponentially many nearly perfect matchings. This generalizes the result and the proof in Combinatorica 11 (3) (1991) 207-218 which is based on the R dl Nibble algorithm (European J. Combin. 5 (1985) 69-78). In this paper, we present a simple proof of Grable's extension of Pippenger's theorem. Our proof is based on a comparison of upper and lower bounds of the probability for a random subgraph to have a nearly perfect matching. We use the Lovasz Local Lemma to obtain the desired lower bound of this probability.
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2.
  • Asratian, Armen S. (författare)
  • Some results on an edge coloring problem of Folkman and Fulkerson
  • 2000
  • Ingår i: Discrete Mathematics. - : Elsevier. - 0012-365X .- 1872-681X. ; 223:1-3, s. 13-25
  • Tidskriftsartikel (refereegranskat)abstract
    • In 1968, Folkman and Fulkerson posed the following problem: Let G be a graph and let (n1,...,nt) be a sequence of positive integers. Does there exist a proper edge coloring of G with colors 1,2,...,t such that precisely ni edges receive color i, for each i=1,...,t? If such a coloring exists then the sequence (n1,...,nt) is called color-feasible for G. Some sufficient conditions for a sequence to be color-feasible for a bipartite graph where found by Folkman and Fulkerson, and de Werra. In this paper we give a generalization of their results for bipartite graphs. Furthermore, we find a set of color-feasible sequences for an arbitrary simple graph. In particular, we describe the set of all sequences which are color-feasible for a connected simple graph G with Δ(G)3, where every pair of vertices of degree at least 3 are non-adjacent.
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  • Resultat 1-2 av 2
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tidskriftsartikel (2)
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refereegranskat (2)
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Asratian, Armen (1)
Kuzjurin, N. N. (1)
Asratian, Armen S. (1)
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Engelska (2)
Forskningsämne (UKÄ/SCB)
Naturvetenskap (2)

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