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Matchings in superpositions of \((n,n)\)-bipartite trees. (English) Zbl 0795.05106

Let \([2n] = \{1, \dots, 2n\}\). Then there are \((2n)^{2n-2}\) labelled trees on \([2n]\). If \([2n]\) is divided into two sets of equal cardinality, say \(L\) and \(D\), then exactly \(n^{2n-2}\) trees have the property that each edge joins a vertex in \(L\) to a vertex in \(D\). Independently choose \(r\) trees from among these trees. \(P_ r (n)\) is defined as the probability that the graph on \([2n]\), that is obtained by taking the union of the edges of the \(r\) trees, contains a perfect matching. It is well known that \(P_ 2(n) \to 1\) as \(n \to \infty\). The main result of the paper is \(1-P_ 2 (n)=O ((\log n)/n)\). Additional, a lower bound is given in \(1-P_ 2(n) > c/n\) with a desired constant \(c>0\) for all sufficiently large \(n\).

MSC:

05C70 Edge subsets with special properties (factorization, matching, partitioning, covering and packing, etc.)
05C05 Trees
05C80 Random graphs (graph-theoretic aspects)
Full Text: DOI

References:

[1] Random Graphs, Academic, New York, 1985, p. 18.
[2] Knuth, Can. J. Math. 20 pp 1077– (1966) · Zbl 0175.21001 · doi:10.4153/CJM-1968-104-8
[3] and , Matching Theory, Annals of Discrete Math 29, North-Holland, Amsterdam, 1986.
[4] Counting labelled trees, Can. Math. Cong., Montreal, 1970. · Zbl 0214.23204
[5] Palmer, J. Comp. Appl. Math 41 pp 199– (1992)
[6] Scoins, Proc. Camb. Phil. Soc. 58 pp 12– (1962)
[7] Walkup, SIAM J. Comput. 8 pp 440– (1979)
[8] Walkup, Disc. Math. 31 pp 59– (1980)
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