For k greater than or equal to l we construct an injection from the set of pairs of matchings in a given graph G of sizes l - 1 and k + 1 into the set of pairs of matchings in G of sizes l and k. This provides a combinatorial proof of the log-concavity of the sequence of matching numbers of a graph. Besides, this injection implies that a certain weighted version of the matching numbers is strongly x-log-concave in the sense of Sagan. (C) 1996 Academic Press, Inc.
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Shanghai Univ Int Business & Econ, Sch Stat & Informat, Shanghai 201620, Peoples R ChinaShanghai Univ Int Business & Econ, Sch Stat & Informat, Shanghai 201620, Peoples R China
Liu, Eric H.
Du, Wenjing
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East China Univ Polit Sci & Law, Wenbo Coll, Shanghai 201620, Peoples R ChinaShanghai Univ Int Business & Econ, Sch Stat & Informat, Shanghai 201620, Peoples R China
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Columbia Univ, Dept Comp Sci, New York, NY 10027 USAColumbia Univ, Dept Comp Sci, New York, NY 10027 USA
Gross, Jonathan L.
Mansour, Toufik
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Univ Haifa, Dept Math, IL-3498838 Haifa, IsraelColumbia Univ, Dept Comp Sci, New York, NY 10027 USA
Mansour, Toufik
Tucker, Thomas W.
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Colgate Univ, Dept Math, Hamilton, NY 13346 USAColumbia Univ, Dept Comp Sci, New York, NY 10027 USA
Tucker, Thomas W.
Wang, David G. L.
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Beijing Inst Technol, Sch Math & Stat, Beijing 102488, Peoples R China
Beijing Key Lab MCAACI, Beijing 102488, Peoples R ChinaColumbia Univ, Dept Comp Sci, New York, NY 10027 USA