RELATIONS AMONG SOME PARAMETERS OF HYPERGRAPHS

The relations among the dominating number, independence number and covering number of hypergraphs are investigated. Main results are as follows：Dv（H）≤min{α≤（H）, p（H）, p（H）, T（H）}; De（H）≤min{v（H）, T（H）, p（H）}; DT（H） ≤αT（H）; S（H）≤ Dv （H） ＋ α（H）≤n; 2≤ Dv （H） ＋ T（H） ≤n; 2 〈 Dv （H） ＋ v（H）≤n/2 ＋ [n/r]; Dv （H） ＋ p（H） 〈_n;2≤De（H） ＋ Dv（H）≤n/2 ＋ [n/r];α（H） ＋ De（H）≤n;2 ≤ De（H） ＋ v（H）≤2[n/r]; 2 De（H） ＋ p（H）≤n-r ＋ 2.     

等距节点上(0,3)插值五次样条

§1.引言 设f(x)是定义在[0,1]上的连续函数,n是自然数。记h=1/n, f_v~((r))=f~((r))(vh),v=0,1,…,n;r=0,1,…,5, f_(v 1/2)~((r))=f~((r))((v 1/2)h),v=0,1,…,n-1;r=0,1,…,5, ω_r(j)=max |f~((r))(x_1)-f~((r))(x_2)|,r=0,1,…,6. |x_1-x_2|≤h 0≤x_1,x_2≤1又设s(x)是[0,1]上满足(i)s(x)∈C~3[0,1],(ii)在[vh,(v 1)h]上s(x)∈∏_5,v=0,1,…,n-1的五次样条.它们的全体记为?_(n5)~((3)) .     

Ramsey Number With Largen

This is an announcement that r(C2m+1, Kn) ≤ c(m) has been proved. The Rarnsey number r(H, Kn) is the smallest integer N such that every H-free graph on N vertices has independence number at least n. The study of Ramsey number r(Ck, Kn) was initiated by Bondy and Erdos[2]. They proved that for any fixed n, r(Ck, Kn) = (k - 1)(n - 1) + 1if k≥n2-1, and r(Ck, Kn)≤kn2. For fixed k≥3, it is difficult to obtain a satisfied bound of r(Ck,Kn) for n →∞. The bound of Bondy and Erdos was improved as r(Ck, Kn)≤c(k)n1+1/m,where m = [(k - 1)/2] by Erdos, Faudree, Rousseau and Schelp[4]. For even cycle, a more refined     

关于补差集与Hadamard矩阵

本文着重讨论了H型补差集,主要结果是: (1) 证明了存在2~i·10~j 18~k·26~r·50~s·82~t阶H型2-补差集;其中i,j,k,r,s,t,为任意非负整数; (2) 给出了71阶和73的H型4-补差集; (3) 定义了v阶Abel群上的C划分, 给出了v=37和61时的C划分,指出了v∈S=S_2∪S_1∪S_3时存在C划分,其中 S_1={2k+1:O≤k≤16}∪{59} S_2={2~i·lO~j·26~k+1:i, j, k为任意非负整数}, S_3={37,61}: (4) 指出了当v′∈S,u∈W=W_1∪W_2∪W_3时,存在v′v阶H型4-补差集,其中 W_1={3~n:n≥1}, W_2={2k+1:0≤k≤14}∪{37,43}, W_3={n:2n-1≡1(mod4)是一素数的方幂}; (5) 利用C划分和[3]的一个结果证明了,当m∈S,n∈W_3时,存在2mn~r(n+1)阶H阵(r≥O); (6) 最后还证明,当在同一个u≡3(mod4)阶Abel群上存在{u;k;λz}差集和{u;1/2(u-1);1/4(u-3)}差集时,且存在v+l=u+1-4(k-λ)阶skew type H阵,则存在uv~r(v+1)阶H阵(r≥O).     

可换序列上,下极值的联合渐近分布

设X_(j,n),1≤j≤N,n=1,2,… 为一r.v.三角阵,X_(1,n),…,X_(N,n)的顺序统计量为 X_(1,n)~*≤X_(2,n)~*≤… ≤X_(N,n)~* [1]考虑了两种情况:(i)N=n,X_(1,n),…,X_(n,n)为可换r.v.无穷序列的一段及(ii)X_(1,n),…,X_(N,n)为i.i.d.r.v.,N=N(n,ω) 为与这些X_(j,n)独立的正整值r.v.,并给出     

Ramsey Number r(C_(2m 1), K_n) With Large n

This is an announcement that r(C2m 1, Kn) ＜ c(m) ( ) 1/m has been proved.The Ramsey number r(H, Kn) is the smallest integer N such that every H-free graph onN vertices has independence number at least n. The study of Ramsey number r(Ck, Kn) wasinitiated by Bondy and Erd s[2]. They proved that for any fixed n, r(Ck, Kn) = (k - 1)(n - 1) 1if k n2 - 1, and r(Ck, Kn) kn2. For fixed k 3, it is difficult to obtain a satisfied bound ofr(Ck, Kn) for n → ∞ . The bound of Bondy and Erd s w…     

ON THE CROSSING NUMBER OF THE COMPLETE TRIPARTITE GRAPH K_(1,8,n)

The well known Zarankiewicz' conjecture is said that the crossing number of the complete bipartite graph Km,n (m≤n) is Z(m,n). where Z(m,n) = [m/2] [(m-1)/2] [n/2] [(n-1)/2](for and real number x, [x] denotes the maximal integer no more than x). Presently, Zarankiewicz' conjecture is proved true only for the case m≤G. In this article, the authors prove that if Zarankiewicz' conjecture holds for m≤9, then the crossing number of the complete tripartite graph K1,8,n is Z(9, n) 12[n/2].     

SPECTRAL RADIUSES OF THE GALTON-WATSON BRANCHING PROCESSES

§1IntroductionSuppose that(X,Px)is a Markov chain on a countable(or finite)state space E.Givenany x,y∈E,we say that y can be reached from x and write x y,if there is n≥1suchthat Px(Xn=y)>0.If x y and y z,then x z.The markov chain X is said to beirreducible if any two states can be reached from each other.(See[1]or[2]).If X isirreducible,then there is a number r,with0≤r≤1,such that lim supn→∞[Px(Xn=y)]n1=r forany x,y∈E.The number r is called the spectral radius of X(refer to[3]).…     

RIGIDITY THEOREMS OF CLIFFORD TORUS

In this article, we prove that the Clifford torus S1(1-r2~(1/2)) × Sn-1(r) is the only closed hypersurface in the unit sphere Sn+1(1) with infinite fundamental group, which satisfy r2 ≥ (n-1)/n, RicM ≤ C-(H), and S ≤ S+(H). Moreover, we give a characterization of Clifford torus S1(1-r2~(1/2)) × Sn-1(r) with r2 = 2(n-1)+nH2±|H| n2H2+4(n-1)(1/2)/2n(1+H2) .     

Turán Number of the Family Consisting of a Blow-up of a Cycle and a Blow-up of a Star

Let F={H₁,...,H_k}(k> 1) be a family of graphs.The Turán number of the family F is the maximum number of edges in an n-vertex {H₁,...,H_k)-free graph,denoted by ex(n,F) or ex(n,{H₁,H₂,...,H_k}).The blow-up of a graph H is the graph obtained from H by replacing each edge in H by a clique of the same size where the new vertices of the cliques are all different.In this paper we determine the Turán number of the family cons...     

关于亲和数的一个注记

本文研究了一类整数序列(2n)2n 1的某些性质,利用费玛数和数论函数的某些性质,获得了验证此类整数是否是亲和数和完全数的方法,既不与其他正整数构成亲和数对也不是完全数.     

The Pseudoachromatic Number of a Graph

The pseudoachromatic number of a graph G is the maximum size of a vertex partition of G (where the sets of the partition may or may not be independent) such that, between any two distinct parts, there is at least one edge of G. This parameter is determined for graphs such as cycles, paths, wheels, certain complete multipartite graphs, and for other classes of graphs. Some open problems are raised.AMS Subject Classification (1991): primary 05C75 secondary 05C85     

Weak Hausdorff Gaps and the 𝔭 ≤ t Problem

We find topological characterizations of the pseudointersection number ?? and the tower number t of the real line and we show that ?? < t iff there exists a compact separable T₂ space X of π-weight < ?? that can be covered by < t nowhere dense sets iff there exists a weak Hausdorff gap of size K < t, i. e., a pair ({A : i ≠ k}, {B_J : j ε K}) C [W]^W X [U]W such that A = {A_i : i ε K} is a decreasing tower, B = {B_j : j ε K) is a family of pseudointersections of A, and there is no pseudointersection S of A meeting each member of B in an infinite set.     

Remarks on restrained domination and total restrained domination in graphs

The restrained domination number ^r(G) and the total restrained domination number _t ^r (G) of a graph G were introduced recently by various authors as certain variants of the domination number (G) of (G). A well-known numerical invariant of a graph is the domatic number d(G) which is in a certain way related (and may be called dual) to (G). The paper tries to define analogous concepts also for the restrained domination and the total restrained domination and discusses the sense of such new definitions.This research was supported by Grant MSM 245100303 of the Ministry of Education, Youth and Sports of the Czech Republic.     

The upper traceable number of a graph

For a nontrivial connected graph G of order n and a linear ordering s: v ₁, v ₂, …, v _n of vertices of G, define . The traceable number t(G) of a graph G is t(G) = min{d(s)} and the upper traceable number t ⁺(G) of G is t ⁺(G) = max{d(s)}, where the minimum and maximum are taken over all linear orderings s of vertices of G. We study upper traceable numbers of several classes of graphs and the relationship between the traceable number and upper traceable number of a graph. All connected graphs G for which t ⁺(G) − t(G) = 1 are characterized and a formula for the upper traceable number of a tree is established. Research supported by Srinakharinwirot University, the Thailand Research Fund and the Commission on Higher Education, Thailand under the grant number MRG 5080075.     

关于调和数的一个结论

设n是大于1的正常数,并且设n=pα11p2α2…ptαt,其中pi为素数,i=1,2,…,t,ω(n)表示n的不同素因子的个数,即ω(n)=t.若n的所有因子的倒数和为整数,即0≤∑ij≤αjj=1,2,…,t1p1i1pi22…ptit为整数,称n是调和数.证明了和调和数相关的一个结论.     

On the relations of graph parameters and its total parameters

In this paper we get some relations between α（G）, α＇（G）, β（G）, β＇（G） and αT（G）, βT（G）. And all bounds in these relations are best possible, where α（G）, α＇（G）,/3（G）, β（G）, αT（G） and βT（G） are the covering number, edge-covering number, independent number, edge-independent number （or matching number）, total covering number and total independent number, respectively.     

Rainbow Numbers for Cycles with Pendant Edges

A subgraph of an edge-colored graph is called rainbow if all of its edges have different colors. For a graph H and a positive integer n, the anti-Ramsey number f (n, H) is the maximum number of colors in an edge-coloring of K _n with no rainbow copy of H. The rainbow number rb(n, H) is the minimum number of colors such that any edge-coloring of K _n with rb(n, H) number of colors contains a rainbow copy of H. Certainly rb(n, H) = f(n, H) + 1. Anti-Ramsey numbers were introduced by Erdős et al. [4] and studied in numerous papers. We show that for n ≥ k + 1, where C _k ⁺ denotes a cycle C _k with a pendant edge.     

A Note on the Bondage Number of a Graph

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