Higher-order matching polynomials and d-orthogonality

We show combinatorially that the higher-order matching polynomials of several families of graphs are d-orthogonal polynomials. The matching polynomial of a graph is a generating function for coverings of a graph by disjoint edges; the higher-order matching polynomial corresponds to coverings by paths. Several families of classical orthogonal polynomials—the Chebyshev, Hermite, and Laguerre polynomials—can be interpreted as matching polynomials of paths, cycles, complete graphs, and complete bipartite graphs. The notion of d-orthogonality is a generalization of the usual idea of orthogonality for polynomials and we use sign-reversing involutions to show that the higher-order Chebyshev (first and second kinds), Hermite, and Laguerre polynomials are d-orthogonal. We also investigate the moments and find generating functions of those polynomials.     

图匹配多项式的因式分解及其应用

通过讨论几类图簇匹配多项式的因式分解,给出了两类图簇匹配等价图的结构性质,从而得到几类新的非匹配唯一图.     

关于路与圈的匹配多项式的一个注记（英文）

The spectra of matching polynomials which are useful in the computations of resonance energy and grand canonical partition functions of molecular's. It also present other properties for certain classes of graphs and lattices. In [1] Balasubramanian calculates several matching polynomials and matching roots of several molecular graphs. He found that the matching polynomial of C_6, C_(10), C_(14), C_(18) and C_(22) are divided by x~2-2. In this note,we prove that x~2-2 divides MC_(4k+2)(x), k = 1, 2,..., n and obtain some other properties of matching polynomials of paths and cycles.     

几类图的匹配等价图类

两个图G和H的匹配多项式相等,则称它们匹配等价.用[G]表示图G的所有不同构的匹配等价图的集合.刻画了匹配次大根小于1的图及这些图的补图的匹配等价图类.     

Herschel图的匹配唯一性

研究了H erschel图的一些性质,以及它的匹配唯一性.     

Defect-d matchings in graphs with cyclomatic numbers 0, 1 and 2

The matching polynomials of chains, circuits and basic graphs with cyclomatic number 2 are used, in order to obtain explicit formulae for the number of detect-d matchings in these graphs.     

On the log-convexity of combinatorial sequences

We give new sufficient conditions for a sequence of polynomials to have only real zeros based on the method of interlacing zeros. As applications we derive several well-known facts, including the reality of zeros of orthogonal polynomials, matching polynomials, Narayana polynomials and Eulerian polynomials. We also settle certain conjectures of Stahl on genus polynomials by proving them for certain classes of graphs, while showing that they are false in general.     

On the theory of the matching polynomial

In this paper we report on the properties of the matching polynomial α(G) of a graph G. We present a number of recursion formulas for α(G), from which it follows that many families of orthogonal polynomials arise as matching polynomials of suitable families of graphs. We consider the relation between the matching and characteristic polynomials of a graph. Finally, we consider results which provide information on the zeros of α(G).     

$R(G)\ge -1$的图族伴随多项式最小根极值的刻画

本文引入了图族伴随多项式的最小根极值,用它刻画了特征标不小于$-1$的图族伴随多项式的最小根极值,给出了其对应的极图, 并由此得到了一些有关这些图族伴随多项式最小根序关系的新结果.     

The genus distributions for a certain type of permutation graphs in orientable surfaces

A circuit is a connected nontrivial 2-regular graph.A graph G is a permutation graph over a circuit C,if G can be obtained from two copies of C by joining these two copies with a perfect matching.In this paper,based on the joint tree method introduced by Liu,the genus polynomials for a certain type of permutation graphs in orientable surfaces are given.     

On chromatic and flow polynomial unique graphs

It is known that the chromatic polynomial and flow polynomial of a graph are two important evaluations of its Tutte polynomial, both of which contain much information of the graph. Much research is done on graphs determined entirely by their chromatic polynomials and Tutte polynomials, respectively. Oxley asked which classes of graphs or matroids are determined by their chromatic and flow polynomials together. In this paper, we found several classes of graphs with this property. We first study which graphic parameters are determined by the flow polynomials. Then we study flow-unique graphs. Finally, we show that several classes of graphs, ladders, Möbius ladders and squares of n-cycle are determined by their chromatic polynomials and flow polynomials together. A direct consequence of our theorem is a result of de Mier and Noy [A. de Mier, M. Noy, On graphs determined by their Tutte polynomial, Graphs Comb. 20 (2004) 105-119] that these classes of graphs are Tutte polynomial unique.     

Genus polynomials and crosscap‐number polynomials for ring‐like graphs

An H‐linear graph is obtained by transforming a collection of copies of a fixed graph H into a chain. An H‐ring‐like graph is formed by binding the two end‐copies of H in such a chain to each other. Genus polynomials have been calculated for bindings of several kinds. In this paper, we substantially generalize the rules for constructing sequences of H‐ring‐like graphs from sequences of H‐linear graphs, and we give a general method for obtaining a recursion for the genus polynomials of the graphs in a sequence of ring‐like graphs. We use Chebyshev polynomials to obtain explicit formulas for the genus polynomials of several such sequences. We also give methods for obtaining recursions for partial genus polynomials and for crosscap‐number polynomials of a bar‐ring of a sequence of disjoint graphs.     

Y(2,2,λ)形图的伴随多项式的分解及其补图的色等价性

构造了两类图簇Y(2,2,λ)∪K1(m为奇数)和Y(2,2,λ)∪EGδ(m为偶数).运用图的伴随多项式,讨论了这两类图簇的伴随多项式的因式分解式,(m=2k-1q-1,λk=(2kq-1)+2k-1qδ),研究了图簇Y(2,2,λk)∪(k-1)K1和Y(2,2,λk)的伴随多项式的因式分解式,进而证明了这些图的补图的色等价性.     

ω_(aδ)~ω∪bω_δ形图簇的伴随分解及其补图的色等价性

研究图的伴随分解及其补图的色等价性.采用伴随多项式的性质讨论图的伴随分解式,通过图的伴随分解式确定其补图的色性.证明了形图簇的伴随多项式的分解定理,从上述定理得到了这类图簇的补图的色等价性.结论通过图的伴随分解研究其补图的色等价性,是有效的途径与方法,从图的伴随分解式容易看出其补图的色等价图的结构规律.     

Tutte-martin polynomials and orienting vectors of isotropic systems

Isotropic systems are structures which unify some properties of 4-regular graphs and of pairs of dual binary matroids. In this paper we unify the properties of the symmetric Tutte polynomials (i.e. with equal variables) of binary matroids and of the Martin polynomials of 4-regular graphs. For this purpose we introduce the orienting vectors of an isotropic system in order to generalize the eulerian orientations of 4-regular graphs.     

σ-polynomials and graph coloring

A new class of graph polynomials is defined. Tight bounds on the coefficients of the polynomials are given, and the exact polynomials for several classes of graphs are derived. The relationship of these polynomials to chromatic polynomials and graph coloring is discussed.     

S~(GS*)类图簇的伴随多项式的因式分解及其色性

通过研究SGS*类图簇的伴随多项式的因式分解,证明了这类图簇的补图的色等价图的结构特征.     

灯笼图的可定向嵌入亏格分布

本文主要利用联树法研究了图的亏格多项式,得到了一类新图(灯笼图)的嵌入亏格分布.证明了灯笼图和偶梯图的亏格分布具有相同的递推关系,从而得到了灯笼图的嵌入亏格分布的精确解.     

Chromatic polynomials,polygon trees,and outerplanar graphs

It is proved that all classes of polygon trees are characterized by their chromatic polynomials, and a characterization is given of those polynominals that are chromatic polynomials of outerplanar graphs. The first result yields an alternative proof that outerplanar graphs are recognizable from their vertex-deleted subgraphs. © 1929 John Wiley & Sons, Inc.     

Rook theory III. Rook polynomials and the chromatic structure of graphs

This paper studies the relationship between the rook vector of a general board and the chromatic structure of an associated set of graphs. We prove that every rook vector is a chromatic vector. We give algebraic relations between the factorial polynomials of two boards and their union and sum, and the chromatic polynomials of two graphs and their union and sum.