Eigenvalues and perfect matchings
نویسندگان
چکیده
منابع مشابه
Perfect matchings, eigenvalues and expansion
In this note, we prove a sufficient condition for the existence of a perfect matching in a regular graph in terms of its eigenvalues and its expansion constant. We improve a recent result of Brouwer and Haemers. French version: Dans cette note, nous prouvons un état suffisant pour l’existence d’un assortiment parfait dans un graphe régulier en termes de ses valeurs propres et son constante d’ex...
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Throughout, G denotes a simple graph of order n (the number of vertices) and size e (the number of edges). The eigenvalues of G are the eigenvalues λi 1 Research partially supported by an NSERC postdoctoral fellowship. 2 Research supported by the Natural Sciences and Engineering Research Council of Canada. Email addresses: [email protected] (Sebastian M. Cioabă), [email protected] (D...
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Let T + 2p be the set of all trees on 2p (p ≥ 1) vertices with perfect matchings. In this paper, we prove that for any tree T in T + 2p , the kth largest eigenvalue λk(T ) satisfies λk(T ) ≤ 1 2 “q ̊ p k ˇ − 1 + q ̊ p k ˇ + 3 ” (k = 1, 2, . . . , p). This upper bound is known to be best possible when k = 1. The set of trees obtained from a tree on p vertices by joining a pendent vertex to each ve...
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In the last decade there have been many results about special families of graphs whose number of perfect matchings is given by perfect or near perfect powers (N. Elkies et al., J. Algebraic Combin. 1 (1992), 111– 132; B.-Y. Yang, Ph.D. thesis, Department of Mathematics, MIT, Cambridge, MA, 1991; J. Propp, New Perspectives in Geometric Combinatorics, Cambridge University Press, 1999). In this pa...
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In 1961, P.W. Kasteleyn enumerated the domino tilings of a 2n × 2n chessboard. His answer was always a square or double a square (we call such a number "squarish"), but he did not provide a combinatorial explanation for this. In the present thesis, we prove by mostly combinatorial arguments that the number of matchings of a large class of graphs with 4-fold rotational symmetry is squarish; our ...
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ژورنال
عنوان ژورنال: Linear Algebra and its Applications
سال: 2005
ISSN: 0024-3795
DOI: 10.1016/j.laa.2004.08.014