Z_n[i]的平方映射图（英文）

本文研究了模n高斯整数环Z_n[i]的平方映射图Γ(n).利用数论、图论与群论等方法,获得了Γ(n)中顶点0及1的入度,并研究了Γ(n)的零因子子图的半正则性.同时,获得了Γ(n)中顶点的高度公式.推广了Somer等人给出的模n剩余类环平方映射图的相关结论.     

随机二又搜索树上顶点数目的极限定理

主要研究大小为n的随机二叉搜索树上3种不同类型的顶点数目.分别以X_n,Y_n和Z_n表示树中含有0,1,2个子点的顶点的数目.在建立X_n递归关系式的基础上,得到了X_n的期望、方差和大数律,并用压缩法证得了X_n的渐近正态性.对于Y_n和Z_n,也得到了类似的结论.     

CCR_n 及 PCR_n 因子关联图中的重边

对补轮换 CCR_n 及纯轮换 PCR_n 因子关联图(?)及Γ~(n)_((x)_0)的研究,对于构造和分析 M 序列有着重要的意义:(?)及Γ~(n)_(x_0)的全部生成树分别对应着全部具最大及最小重量的 n 阶 M 序列;它们中的重边替换与用自同构产生的小项更迭给出了构造 M 序列的途径;而(?)中环的裂分又可给出其它重量的 n 阶 M 序列;这种生成树的方法还可与剪接法结合得到一种更快速的剪接——生成树法.本文在[1,4—6]的基础上从另一     

地图着色定理与图的曲面嵌入(Ⅱ)

<正> 六、电流图 定义6.1.一个图Z,如果对于一个n阶Abel加法群Z_n,不妨就取它为modn的整数群,满足下面四个条件IC1,IC2,IC3,IC4就称之为Z_?的第一类电流图.并记之为Z_n(I). IC1,Z的所有顶点的次非3即1. IC2,有α_1=[n/2]条边与群元素1,2,…,[n/2],作为电流,一一对应,使得悬挂边(即有次为1的端点)上的电流k与n互素,即(k,n)=1.还可赋次为1的顶点以符     

群环Z_nG的基于理想△(G)的零因子图

主要讨论了群环Z_nG的基于理想△(G)的零因子图Γ_(△(G))(Z_nG)的性质,分别给出了Γ_(△(G))(Z_nG)的围长,平面性和直径的详细刻画.同时,给出了交换环R基于其理想I的零因子图Γ_I(R)与商环R/I的零因子图Γ(R/I)的直径的关系的一个刻画.     

关于具有给定非悬挂边数的树的极小能量

图的能量定义为其特征的绝对值之和.Γ(n,q)表示所有具有n个顶点,q条非悬挂边的树构成的集合.本文中,我们利用两个变换确定了Γ(n,q)中具有极小、第二小能量的树.     

圆周自映射的v极限集

设 f:s~1→s~1为连续映射。f 的回归点集和非游荡集分别记为 R 和Ω.xes~1,令v(x)=ω(x)∩α(x),其中ω(x)(α(x)为 x 的ω-(α-)极限集.令Γ=(?)v(x),若 y(?)s~1,记∧(y)=(?)ω(x).我们证明了:(1)Γ=∧(Ω)=∧(∧)=∧(Γ);(2)Ω-Γ是 s~1中无处稠密的可数集;(3)若以 x 为端点的每个开弧至少包含某个轨道中的的两点,则 x∈Γ;(4)若Γ-R≠φ,则Γ-R 为不可数集;(5)如(?)-R≠φ,则(?)-R 为无限集;(6)Γ=R 当且仅当(?)~(+)∩(?)~(-)=R.其中(?)~(+)((?)~(-))表示 R 的右(左)闭包。     

关于解析函数的一个唯一性定理及其应用

<正> §1.在近代解析函数论中边界值的唯一性定理有许多的研究,其中有我们所习知著名的(?)氏唯一性定理,即:若 D 是某一可求长约当曲线Γ所范围的内域,而 f(z)是 D 内的半纯函数,如在Γ上存在某一测度大于零的集 E_z,对 E_z 任一点 z_0 上,f(z)的角形边界值为零.则必致f(z)≡0于 D 内.同时,卢洵(?)与普里瓦洛夫还指出:存在有单位圆域内非常数的解析函数,而在一个正测度的集(?)上具有等于零的射形边界值.除此之外还有一个很有用的 Koebe 氏定理.即:     

广义Carmichael数

设n是一个合数,Z_n表示模n的剩余类环,r(x)∈Z_n[x]是一个首一的k(>0)次不可约多项式。本文引入n是k阶摸r(x)的Carmichael数的定义,全体这样的数记为集C_(k,r)(x),由此给出k阶Carmichael数集:C_k={∪C_(k,r)(x)|r(x)过全体Z_n上的首一k次不可约多项式}。显然C_1表示通常的Carmichael数集。作者得到了n∈C_(k,r(x))的一个充要条件,进而得到n∈C_k的一个充要条件及n∈C_2的一个更易计算的充要条件,还证明了C_1(?)C_2以及|C_2|=∞。     

双曲问题边界条件的均匀化

本文对于双曲问题讨论边界条件的均匀化问题。设边界=(?)Ω可表为Γ=Γ_1∪Γ_2∪Γ_3,Γ_1∩Γ_3=φ。(?)ε>0,将分为和,並在其上给出不同的边界条件。我们对于几种不同的情形讨论了随的来种测度趋于零时(当ε→0时)解的极限性态。     

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.     

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$Γ^n_R$.     

Heptavalent Symmetric Graphs with Certain Conditions

A graph Γ is said to be symmetric if its automorphism group Aut(Γ)acts transitively on the arc set of Γ.We show that if Γ is a finite connected heptavalent symmetric graph with solvable stabilizer admitting a vertex-transitive non-abelian simple group G of automorphisms,then either G is normal in Aut(Γ),or Aut(Γ)contains a non-abelian simple normal subgroup T such that G≤T and(G,T)is explicitly given as one of 11 possible exceptional pairs of non-abelian simple groups.If G is arc-transitive,then G is always normal in Aut(r),and if G is regular on the vertices of Γ,then the number of possible exceptional pairs(G,T)is reduced to 5.     

Bipartite double cover and perfect 2-matching covered graph with its algorithm

Let B(G) denote the bipartite double cover of a non-bipartite graph G with v≥2 vertices and ? edges. We prove that G is a perfect 2-matching covered graph if and only if B(G) is a 1-extendable graph. Furthermore, we prove that B(G) is a minimally 1-extendable graph if and only if G is a minimally perfect 2-matching covered graph and for each e = xy ∈ E(G), there is an independent set S in G such that |Γ_G(S)| = |S| + 1, x ∈S and |Γ_G-xy(S) | = |S|. Then, we construct a digraph D from B(G) or G and show that D is a strongly connected digraph if and only if G is a perfect 2-matching covered graph. So we design an algorithm in O(v?) time that determines whether G is a perfect 2-matching covered graph or not.     

Collapsible graphs and reductions of line graphs

A graph G is collapsible if for every even subset X⊆V(G), G has a subgraph Γ such that G−E(Γ) is connected and the set of odd-degree vertices of Γ is X. A graph obtained by contracting all the non-trivial collapsible subgraphs of G is called the reduction of G. In this paper, we characterize graphs of diameter two in terms of collapsible subgraphs and investigate the relationship between the line graph of the reduction and the reduction of the line graph. Our results extend former results in [H.-J. Lai, Reduced graph of diameter two, J. Graph Theory 14 (1) (1990) 77-87], and in [P.A. Catlin, Iqblunnisa, T.N. Janakiraman, N. Srinivasan, Hamilton cycles and closed trails in iterated line graphs, J. Graph Theory 14 (1990) 347-364].     

Edge-distance-regular graphs

Edge-distance-regularity is a concept recently introduced by the authors which is similar to that of distance-regularity, but now the graph is seen from each of its edges instead of from its vertices. More precisely, a graph Γ with adjacency matrix A is edge-distance-regular when it is distance-regular around each of its edges and with the same intersection numbers for any edge taken as a root. In this paper we study this concept, give some of its properties, such as the regularity of Γ, and derive some characterizations. In particular, it is shown that a graph is edge-distance-regular if and only if its k-incidence matrix is a polynomial of degree k in A multiplied by the (standard) incidence matrix. Also, the analogue of the spectral excess theorem for distance-regular graphs is proved, so giving a quasi-spectral characterization of edge-distance-regularity. Finally, it is shown that every nonbipartite graph which is both distance-regular and edge-distance-regular is a generalized odd graph.     

Mean distance in a graph

The average or mean of the distances between vertices in a connected graph Γ, μ(Γ), is a natural measure of the compactness of the graph. In this paper we compute bounds for μ(Γ) in terms of the number of vertices in Γ and the diameter of Γ. We prove a formula for computing μ(Γ) when Γ is a tree which is particularly useful when Γ has a high degree of symmetry. Finally, we present algorithms for μ(Γ) which are amenable to computer implementation.     

On CCE graphs of doubly partial orders

Let D be a digraph. The competition-common enemy graph (CCE graph) of D has the same set of vertices as D and an edge between vertices u and v if and only if there are vertices w and x in D such that (w,u), (w,v), (u,x), and (v,x) are arcs of D. We call a graph a CCE graph if it is the CCE graph of some digraph. In this paper, we show that if the CCE graph of a doubly partial order does not contain C₄ as an induced subgraph, it is an interval graph. We also show that any interval graph together with enough isolated vertices is the CCE graph of some doubly partial order.     

Some Remarks on the Graph Γ I (R)

Let R be a commutative ring with nonzero identity and Z(R) its set of zero-divisors. The zero-divisor graph of R is Γ(R), with vertices Z(R)?{0} and distinct vertices x and y are adjacent if and only if xy = 0. For a proper ideal I of R, the ideal-based zero-divisor graph of R is Γ _I (R), with vertices {x ∈ R?I | xy ∈ I for some y ∈ R?I} and distinct vertices x and y are adjacent if and only if xy ∈ I. In this article, we study the relationship between the two graphs Γ(R) and Γ _I (R). We also determine when Γ _I (R) is either a complete graph or a complete bipartite graph and investigate when Γ _I (R) ? Γ(S) for some commutative ring S.     

Simple Minimum (K4-e)-coverings of Complete Multipartite Graphs

A decomposition of K_(n(g))∪Γ, the complete n-partite equipartite graph over gn vertices union a graph Γ(called the excess) that is a subgraph of K_(n(g)), into edge disjoint copies of a graph G is called a simple minimum group divisible covering of type g~n with G if Γ contains as few edges as possible. We examine all possible excesses for simple minimum group divisible(K_4-e)-coverings.Necessary and sufficient conditions are established for their existence.