酉群上Fourier级数的Cesaro求和

设un为n阶酉群。u∈L1(Un)的Fourier级数的第二型Cesáro平均为σNα(u,U)=KN*αu(U),其中 KNα(U)=sum from (N≥li>…>ln≥-N)(Al1α…A1uN(f)Xf(U)),U∈Un为相应的核函数。本文给出“Lebesgue常数”‖KNα‖(L1(Un))的精确估计,并由此建立了酉群上函数的Fourier级数按第二型Cesáro求和收敛于自身的条件。     

无限箭图的同调群

对任意箭图Q,我们研究路代数A=kQ的Hochschild同调群H_n(A)和同调群Tor_n^Ae(A,A),其中A^e是代数A的包络代数。在本文中,我们具体地给出了各次同调群和Hochschild同调群。     

关于切点单形的两个不等式

Definition Let A_i(i=1,2,…,n+1) be the vertex of a simplex Σ_A in n-dimen-sional Euclidean space Eⁿ and A_i′ be the tangent points which the inscribed sphere of Σ_A is tangent to the side face of Σ_A, then the simplex with the tangent points as vertexes is called the tangent points simplex.     

概率密度的均匀核估计与近邻估计的均方误差

In this paper we consider the Mean Square Error (MSE) of two uaual estimates of density function f(x) at a point x: The uniform kernel estimate f_n(x) and the NN estimate fn(x). we- show that when f is differentiable for sufficiently high order at x. these MSE can be expanded in a form E(f_n(x)-f(x))²=A₁(x)n^-4/5 +A₂(x)n^-1+A₃(x)n^-6/5+…;E(f_n(x)-f(x))²=B₁(x)n^-4/5 +B₂(x)n^-1+B₃(x)n^-6/5+… And if we suitably choose the parameters in f_n and f_n to make A₁(x) and B₁(x)to assume its minimunm value, then we also, have A₂(x) =B₂(x) but A₃(X) differs form B₃(X). This result shows that while the two estimates are not identical with respect to MSE. each one can be superior to the other in various special cases.     

算子方程的解及算子张量积

本文讨论Hilbert空间上一类三阶二元算子方程组A^*AC = αA^*A² + βAA^*A;AA^*C = λA^*A² + γAA^*A,给出所有重交换的解(A,C).作为应用,得到算子张量积A(?)B+C(?)D和A₁(?)A₂(?)…(?)A_n为拟正规算子的充分必要条件.     

典型群的增广商群

设G 为有限域K 上的一般线性群(特殊线性群、酉群、辛群及正交群), 记整群环ZG 的n 次增广理想为△ⁿ(G). 本文着重研究有限域上的典型群的增广商群Q_n(G) = △ⁿ(G)/△ⁿ⁺¹(G), 并刻画了这些连续商群的结构.     

右半平面内解析函数的准确零(R)级

Let f(s)=(?)a_ne^-λ_m3(s=σ+it),0<λ_n↑+∞), where (?)(n/logU(λ_n))=E<+∞,(?)(log|α_n|/λ_n)=0.     

有限域上长为2mpn 的负循环码

设F_q 是奇数阶有限域. 本文主要借助X^2mpn+1 在F_q 上的不可约因式分解来确定有限域F_q上所有长为2^mpⁿ 的负循环码和自对偶的负循环码的生成多项式, 这里p 是q-1 的奇素因子, m 和n是正整数.     

某些周期卷积类的宽度及单边宽度的精确估计

本文解决了由引入的一族周期卷积类κ_q(ψ)(1≤q≤+∞)在L尺度下以n—1阶三角多项式子空间T_n-。最佳单边逼近E_n⁺(κ_q(ψ))_L的精确估计。     

Heisenberg群上无穷远处的集中列紧原理和具有Sobolev临界指数的p - 次Laplace方程多解的存在性

通过建立Heisenberg群上无穷远处的集中列紧原理, 研究了如下$p$ -次Laplace方程 -Δ_{H, p}u=λg(ξ)|u|^q-2u+f (ξ)|u|^p*-2u,在Hⁿ上, u∈ D^{1, p}(Hⁿ), 其中ξ∈Hⁿ,λ∈R,1j, 且m, j为整数.     

On Commuting Graph of Group Ring $Z_nS_3$

The commuting graph of an arbitrary ring $R$, denoted by $Γ(R)$, is a graph whose vertices are all non-central elements of $R$, and two distinct vertices $a$ and $b$ are adjacent if and only if $ab = ba$. In this paper, we investigate the connectivity and the diameter of $Γ(Z_n S_3)$. We show that $Γ(Z_n S_3)$ is connected if and only if $n$ is not a prime number. If $Γ(Z_n S_3)$ is connected then diam $(Γ(Z_n S_3)) = 3$, while if $Γ(Z_n S_3)$ is disconnected then every connected component of $Γ(Z_n S_3)$ must be a complete graph with same size, and we completely determine the vertice set of every connected component.     

给定顶点数和边数的连通图的Q-谱半径的界

图的无符号拉普拉斯矩阵是图的邻接矩阵和度对角矩阵的和,其特征值记为q1≥q2≥…≥qn.设C(n,m)是由n个顶点m条边的连通图构成的集合,这里1≤n-1≤m≤(n2).如果对于任意的G∈C(n,m)都有q1(G*)≥q1(G)成立,图G*∈C(n,m)叫做最大图.这篇文章证明了对任意给定的正整数a=m-n+1,如果n...     

On the fixing sets of dihedral groups

The fixing number of a graph $\Gamma$ is the minimum number of labeled vertices that, when fixed, remove all nontrivial automorphisms from the automorphism group of $\Gamma$. The fixing set of a finite group $G$ is the set of all fixing numbers of graphs whose automorphism groups are isomorphic to $G$. Previously, authors have studied the fixing sets of both abelian groups and symmetric groups. In this article, we determine the fixing set of the dihedral group.     

偶特征有限域上对称矩阵结合方案

设S(n,q)是偶特征有限域F_q上n×n对称矩阵所成的集合.令R_i={(X,Y)|X,Y∈S(n,q),rank(Y-X)=2i-1,2i},0≤i≤[(n+1)/2]采用矩阵方法,证明了Sym(n,q)={s(n,q),{R_i}_(0≤i≤)[(n+1)/2]}是[(n+1)/2]个结合类的P—多项式对称结合方案,而Sym(n,q)的结合关系的图Γ~((1))是正则的,并且它同构于交错矩阵结合方案.此外,又给出Sym(n,q)的自同构形式.     

模n剩余类环零因子图的一些性质

模n剩余类环Z_n的零因子图记为Γ(Z_n),其顶点为Z_n的所有非零零因子,两个不同的顶点x与y有一条边相连当且仅当xy=0.对Γ(Zn)和(?)的欧拉性及一笔画性进行了探讨,完全确定了当n为何值时,Γ(Z_n)和(?)为欧拉图或是一笔画图.     

Counting the number of independent sets in chordal graphs

We study some counting and enumeration problems for chordal graphs, especially concerning independent sets. We first provide the following efficient algorithms for a chordal graph: (1) a linear-time algorithm for counting the number of independent sets; (2) a linear-time algorithm for counting the number of maximum independent sets; (3) a polynomial-time algorithm for counting the number of independent sets of a fixed size. With similar ideas, we show that enumeration (namely, listing) of the independent sets, the maximum independent sets, and the independent sets of a fixed size in a chordal graph can be done in constant time per output. On the other hand, we prove that the following problems for a chordal graph are #P-complete: (1) counting the number of maximal independent sets; (2) counting the number of minimum maximal independent sets. With similar ideas, we also show that finding a minimum weighted maximal independent set in a chordal graph is NP-hard, and even hard to approximate.     

Rank-determining sets of metric graphs

A metric graph is a geometric realization of a finite graph by identifying each edge with a real interval. A divisor on a metric graph Γ is an element of the free abelian group on Γ. The rank of a divisor on a metric graph is a concept appearing in the Riemann-Roch theorem for metric graphs (or tropical curves) due to Gathmann and Kerber, and Mikhalkin and Zharkov. We define a rank-determining set of a metric graph Γ to be a subset A of Γ such that the rank of a divisor D on Γ is always equal to the rank of D restricted on A. We show constructively in this paper that there exist finite rank-determining sets. In addition, we investigate the properties of rank-determining sets in general and formulate a criterion for rank-determining sets. Our analysis is based on an algorithm to derive the v₀-reduced divisor from any effective divisor in the same linear system.     

Kp,q-factorization of complete bipartite graphs

Let K_(m,n) be a complete bipartite graph with two partite sets having m and nvertices, respectively. A K_(p,q)-factorization of K_(m,n) is a set of edge-disjoint K_(p,q)-factorsof K_(m,n) which partition the set of edges of K_(m,n). When p=i and q is a prime number,Wang, in his paper "On K_(1,k)-factorizations of a complete bipartite graph" (Discrete Math,1994, 126; 359-364), investigated the K_(1,q)-factorization of K_(m,n) and gave a sufficientcondition for such a factorization to exist. In the paper "K_(1,k)-factorizations of completebipartite graphs" (Discrete Math, 2002, 259: 301-306), Du and Wang extended Wang'sresult to the case that q is any positive integer In this paper, we give a sufficient conditionfor K_(m,n) to have a K_(p,q)-factorization. As a special case, it is shown that the Martin's BACconjecture is true when p: q=k: (k+1) for any positive integer k.     

无爪3 -正则图的独立数

如果图G的一个集合X中任两个点不相邻, 则称 X 为独立集合. 如果 N[X]=V(G), 则称X是一个控制集合. i(G)(β(G))分别表示所有极大独立集合的最小(最大)基数. γ(G)(Γ(G))表示所有极小控制集合的最小(最大)基数. 在这篇论文中, 作者证明如下结论: (1) 如果 G ∈R 且G 是n阶3 -正则图, 则 γ(G)= i(G), β(G)=n/3. (2) 每个n阶连通无爪3 -正则图 G, 如果 G(G≠ K₄) 且不含诱导子图K₄-e, 则 β(G) =n/3.     

Domination in Generalized Cayley Graph of Commutative Rings

Let $R$ be a commutative ring with identity and $n$ be a natural number. The generalized Cayley graph of $R$, denoted by $Γ^n_R$, is the graph whose vertex set is $R^n$\{0} and two distinct vertices $X$ and $Y$ are adjacent if and only if there exists an $n×n$ lower triangular matrix $A$ over $R$ whose entries on the main diagonal are non-zero such that $AX^T=Y^T$ or $AY^T=X^T$, where for a matrix $B$, $B^T$ is the matrix transpose of $B$. In this paper, we give some basic properties of$Γ^n_R$ and we determine the domination parameters of$Γ^n_R$.