Acyclic orientations and poly-Bernoulli numbers
Acyclic orientations and poly-Bernoulli numbers
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无环取向和聚伯努利数
DOI:
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发表时间:
2014
期刊:
影响因子:
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通讯作者:
R. Schumacher
中科院分区:
文献类型:
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作者:
P. Cameron;C. Glass;Kamilla Rekv'enyi;R. Schumacher
In 1997, Masanobu Kaneko defined \emph{poly-Bernoulli numbers}, which bear much the same relation to polylogarithms as Berunoulli numbers do to logarithms. In 2008, Chet Brewbaker described a counting problem whose solution can be identified with the poly-Bernoulli numbers with negative index, the \emph{lonesum matrices}.
The main aim of this paper is to give formulae for the number of acyclic orientations of a complete bipartite graph, or of a complete bipartite graph with one edge added or removed.
Our formula shows that the number of acyclic orientations of $K_{n_1,n_2}$ is equal to the poly-Bernoulli number $B_{n_1}^{(-n_2)}$. We also give a simple bijective identification of acyclic orientations and lonesum matrices.
We make some remarks on the context of our result, which are expanded in another paper.