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arXiv 1105.2202cs.DMmath.CO
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关于独立多项式的对称性

On Symmetry of Independence Polynomials

Vadim E. Levit, Eugen Mandrescu

摘要:

图中的独立集是指图中两两不相邻顶点的集合,α(G)是图G中最大独立集的大小.匹配是一组非关联边,而mu(G)是最大匹配的基数。如果s_{k}是G中基数k的独立集的数量,则I(G;x)= s_{0} + s_{1} x+ s_{2} x^{2}+.+ s_{α(G)} x^{α(G)}称为G的独立多项式(Gutman and Harary,1983)。如果$s_{j}=s_{α-j}$,0=< j =< alpha(G),则I(G;x)称为对称的(或回文的)。已知图G*2 K_{1}是通过将G的每个顶点连接到两个新的顶点而得到的,具有对称独立多项式(Stevanovic,1998)。本文证明了对任意图G和任意非负整数k =< mu(G),可以构造图H,使得G是H的子图,I(H;x)是对称的,且I(G*2 K_{1} ;x)=(1+x)^{k}*I(H;x).

英文摘要:

An independent set in a graph is a set of pairwise non-adjacent vertices, and alpha(G) is the size of a maximum independent set in the graph G. A matching is a set of non-incident edges, while mu(G) is the cardinality of a maximum matching. If s_{k} is the number of independent sets of cardinality k in G, then I(G;x)=s_{0}+s_{1}x+s_{2}x^{2}+...+s_{α(G)}x^{α(G)} is called the independence polynomial of G (Gutman and Harary, 1983). If $s_{j}=s_{α-j}$, 0=< j =< alpha(G), then I(G;x) is called symmetric (or palindromic). It is known that the graph G*2K_{1} obtained by joining each vertex of G to two new vertices, has a symmetric independence polynomial (Stevanovic, 1998). In this paper we show that for every graph G and for each non-negative integer k =< mu(G), one can build a graph H, such that: G is a subgraph of H, I(H;x) is symmetric, and I(G*2K_{1};x)=(1+x)^{k}*I(H;x).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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