关于临界图的一个定理的推广

叶宏博证明了当Δ≥５时没有度序列是２ｒΔ２ｒ的Δ－临界图．Ｋａｙａｔｈｒｉ推广了上述结果,证明了当Δ≥５时,没有同时满足下列两个条件的Δ－临界图：（ａ）Ｇ有一个２度点ｘ;设ｙ,ｚ是ｘ的两个邻接点;（ｂ）有一主项点ｙ１∈ＮＧ（ｙ）（ｙ１≠ｙ）与－２度点邻接．我们对上述结果进一步推广,证明了条件（ｂ）不是必要的;只要ｙ１与一个度数小于Δ－１的点邻接即可（可以不是２度点）．     

关于Laplace分布的一个强极限定理

利用似然比构造几乎处处收敛的上鞅 ,结合分析方法 ,给出了 Laplace分布的一个强极限定理 .     

T-型树谱唯一性的一个简单刻画

图G称为谱唯一的,如果任何与G谱相同的图一定与G同构.一棵树称为T-型树如果其仅有一个最大度为3的顶点.本文给出了T-型树谱唯一性的一个简单刻画,从而完全解决了T-型树的谱唯一性问题.     

关于混合图的谱扰动

本文刻画了如下的混合图:在添加一个环时,它恰有一个 Laplace特征值以整数增加,其它的 Laplace特征值保持不变.本文是文章[Linear Algebra and its Applications 374(2003):307-316]的一个延续性的文章.     

关于推广的积分中值定理的一个注记

本文在一般情况下讨论了推广的积分中值定理“中间点”的渐近性 ,从而给出了具有普遍意义的结果 .     

关于Laplace分布的一个强极限定理

利用似然比构造几乎处处收敛的上鞅,结合分析方法,给出了Ｌａｐｌａｃｅ分布的一个强极限定理。     

一个伴随等价定理的推广及其简证

记 Gr为任意图 G的 r个拷贝中的对应点 ( r个 )分别与星图 Sr+ 1 的 r个 1度点粘接后得到的图 ,又记 H r为该图 G的相应点与星图 Sr+ 1 的 r度点粘接后得到的图 .如果 G不含三角形 ,则图 ( r- 1) K1 ∪ Gr和图 ( r- 1) G∪ H r伴随等价 ,进而它们的补图色等价     

关于Orlicz-Pettis定理的一个推广

研究了局部凸空间中级数无条件收敛和子级数收敛的各种等价形式,证明了Orlicz-Pettis定理在局部凸空间中一般拓扑意义下仍成立,并且利用此结果刻划了取值于局部凸空间的强可加矢值测度.     

关于等腰三角形定理的一个推广

1.大家很熟悉,若在△ABc中乙A=艺B,则其所对的边相等。二b.在这里我们要征明,若△才Bc的角之简的关系为A“砧,则其边之简的依从关系为 f。(a,石,e)二。,(1)其中,是整数,j,;缝某个多项式(不高于2,阶),‘它对于旅一个。都是确定的.当二二1时(郎当A二B时)关系式(功为4一b=0的形式.歌。=2,邹哎=ZBM,使得乙‘才M=乙盯B汪1、.在BC边上取一点汉刀是角汉的平分橇).△才Bc的△凡I月C;因此 C石AM MC尽,由此,b、:,一警和、。一答.又因为△A、。是等腰三角形,所以BM一AM=。,郎 aZ一石2 bc 下一石一-一丁二0,或 少2(a,b,c)=be一、2+占2二0.这…     

图的Laplace谱半径的几类上界

本文得到图的Laplace谱半径的几类上界.通过选取适当的对角矩阵,我们得到了在一定程度上优于其他界的上界.     

图的规范拉普拉斯谱与优超（英文）

令G是简单图.记L(G)为图G的规范拉普拉斯矩阵,其特征值称为图的规范拉普拉斯特征值.[Adv.Math.(China),2017,46(6):848-856]给出了关于规范拉普拉斯特征值和的相关结论,并提出相关猜想.我们发现在上述文章中的一些重要结果中存在一些错误.本文修正了所有不正确的结果.此外,我们讨论了￡(G)的特征值优超不等式.利用这些结果,我们证实了[Adv.Math.(China),2017,46(6):848-8561中提出的一个猜想.     

Some Results on the Majorization Theorem of Connected Graph

Let π = (d1, d2, . . . , dn) and π'= (d1', d2' , . . . , d'n) be two non-increasing degree sequences. We say π is majorizated by π' , denoted by π△π , if and only if π≠π , Σni=1di=Σni=1d'i , and Σji=1di ≤Σji=1di for all j = 1, 2, . . . , n. We use Cπ to denote the class of connected graphs with degree sequence π. Let ρ(G) be the spectral radius, i.e., the largest eigenvalue of the adjacent matrix of G. In this paper, we extend the main results of [Liu, M. H., Liu, B. L., You, Z. F.: The majorization theorem of connected graphs. Linear Algebra Appl., 431(1), 553-557 (2009)] and [Biyikoglu, T., Leydold, J.: Graphs with given degree sequence and maximal spectral radius. Electron. J. Combin., 15(1), R119 (2008)]. Moreover, we prove that if π and π' are two different non-increasing degree sequences of unicyclic graphs with ππ' , G and G' are the unicyclic graphs with the greatest spectral radii in Cπ and Cπ' , respectively, then ρ(G) ρ(G').     

一类单圈图的拉普拉斯谱刻画

Let H（n; q, n1, n2, n3, n4） be a unicyclic graph with n vertices containing a cycle Cq and four hanging paths Ph1＋1, Pn2＋1, Pn3＋1 and Pn4＋1 attached at the same vertex of the cycle. In this paper, it is proved that all unicyclic graphs H （n; q, n1, n2, n3, n4） are determined by their Laplacian spectra.     

On the Laplacian energy of a graph

In this paper we consider the energy of a simple graph with respect to its Laplacian eigenvalues, and prove some basic properties of this energy. In particular, we find the minimal value of this energy in the class of all connected graphs on n vertices (n = 1, 2, ...). Besides, we consider the class of all connected graphs whose Laplacian energy is uniformly bounded by a constant α ⩾ 4, and completely describe this class in the case α = 40.     

图的剖分点-边冠运算下的规范拉普拉斯谱

A subdivision vertex-edge corona G_1~S?(∪ G_3~E) is a graph that consists of S(G_1),|V(G_1)| copies of G_2 and |I(G_1)| copies of G_3 by joining the i-th vertex in V(G_1) to each vertex in the i-th copy of G_2 and i-th vertex of I(G_1) to each vertex in the i-th copy of G_3.In this paper, we determine the normalized Laplacian spectrum of G_1~S?(G_2~V∪ G_3~E) in terms of the corresponding normalized Laplacian spectra of three connected regular graphs G_1, G_2 and G_3. As applications, we construct some non-regular normalized Laplacian cospectral graphs. In addition, we also give the multiplicative degree-Kirchhoff index, the Kemeny's constant and the number of the spanning trees of G_1~S?(G_2~V∪ G_3~E) on three regular graphs.     

The Spectrum of a Random Geometric Graph is Concentrated

Consider n points, x ₁,... , x _n , distributed uniformly in [0, 1] ^d . Form a graph by connecting two points x _i and x _j if . This gives a random geometric graph, , which is connected for appropriate r(n). We show that the spectral measure of the transition matrix of the simple random walk on is concentrated, and in fact converges to that of the graph on the deterministic grid.      

Remarks on Q-integral complete multipartite graphs

A graph is Q-integral if the spectrum of its signless Laplacian matrix consists entirely of integers. In their study of Q-integral complete multipartite graphs, [Zhao et al., Q-integral complete r-partite graphs, Linear Algebra Appl. 438 (2013) 1067–1077] posed two questions on the existence of such graphs. We resolve these questions and present some further results characterizing particular classes of Q-integral complete multipartite graphs.     

Spectra of Corona Based on the Total Graph

For two simple connected graphs $G_1$ and $G_2$, we introduce a new graph operation called the total corona $G_1⊛G_2$ on $G_1$ and $G_2$ involving the total graph of $G_1.$ Subsequently, the adjacency (respectively, Laplacian and signless Laplacian) spectra of $G_1⊛G_2$ are determined in terms of these of a regular graph $G_1$ and an arbitrary graph $G_2.$ As applications, we construct infinitely many pairs of adjacency (respectively, Laplacian and signless Laplacian) cospectral graphs. Besides we also compute the number of spanning trees of $G_1⊛G_2.$     

A New Lower Bound for the Kirchhoff Index using a numerical procedure based on Majorization Techniques

In this note, we use a procedure, proposed in [Bianchi, M., and A. Torriero, Some localization theorems using a majorization technique, Journal of Inequalities and Applications 5 (2000), 433–446], based on a majorization technique, which localizes real eigenvalues of a matrix of order n. Through this information, we compute a lower bound for the Kirchhoff index (see [Bianchi M., A. Cornaro, J.L. Palacios and A. Torriero, Bounds for the Kirkhhoff index via majorization techniques, Journal of Mathematical Chemistry, (2012) online first]) that takes advantage of additional eigenvalues bounds. An algorithm has been developed with MATLAB software to evaluate the above mentioned bound. Finally, numerical examples are provided showing how tighter results can be obtained.     

Bounds and Majorization Relations for the Zeros of Polynomials

We use matrix inequalities to prove several bounds and majorization relations for the zeros of polynomials. Our results generalize the classic bound of Montel and improve some other known bounds.