完备流形上拉普拉斯算子的L2特征形式

本文研究了完备非紧流行上拉普拉斯算子的L²特征形式.利用应力能量张量的方法,得到在此类流形上拉普拉斯算子的L²特征形式的一些不存在性定理。     

凹函数定义的弱Orlicz-Hardy空间之间的鞅变换

本文研究了两个弱Orlicz-Hardy鞅空间中元素之间相互转换关系的问题.利用鞅变换的方法,证明了：设φ₁是凹Young函数,φ₂是凹或者凸Young函数,且q_φ1 > 0,0 < q_φ2≤p_φ2 <+∞,则当φ₁≤φ₂时,wH_φ1中的元素是wH_φ2中元素的鞅变换的结果,所得结果将已有的相关结论由强型空间（赋范空间）推广到弱型空间（赋拟范空间）.     

Gorenstein平坦(余挠)维数和Hopf作用

设H是域k上的有限维Hopf代数,A是左H-模代数.本文研究了Gorenstein平坦（余挠）维数在A-模范畴和A#H-模范畴之间的关系.利用可分函子的性质,证明了（1）设A是右凝聚环,若A#H/A可分且φ：A→A#H是可裂的（A,A）-双模同态,则l：Gwd（A）=l：Gwd（A#H）;（2）若A#H/A可分且φ：A→A#H是可裂的（A,A）-双模同态,则l：Gcd（A）=l：Gcd（A#H）,推广了斜群环上的结果.     

一类新的有限域上的置换多项式

本文研究了有限域上置换多项式的构造问题.利用分段方法构造了F_q²上形如（x^q-x+c）^{（k（q2-1））/（d）+1}+x^q+x的置换多项式,其中1≤k < d且d是q-1的任意因子,推广了已有文献中的某些结果.     

半粘合诱导的t-结构

本文研究了对于给定的一个三角范畴的上（下）粘合（C'',C,C"）,如何由C的一个t-结构诱导C''和C"的t-结构的问题.利用左（右）t-正合函子的概念,给出了由C的一个t-结构可诱导出C''和C"的t-结构的充分条件.将粘合的一些相关结果推广到了上（下）粘合的情形.     

二部图的距离k次方和问题

本文定义S_k（G）为G中所有点对之间距离的k次方之和.利用顶点划分的方法得到了直径为d的n顶点连通二部图S_k（G）的下界,并确定了达到下界所对应的的极图.     

关于半对偶化模的Gorenstein模的稳定性

本文研究了相对于半对偶化模C的Gorenstein模（即Gorenstein C-投射模,Gorenstein C-内射模和Gorenstein C-平坦模）的稳定性的问题.利用同调的方法,获得了Gorenstein C-投射（C-内射,C-平坦）模具有很好的稳定性的结果,推广了Gorenstein投射（内射,平坦）模具有很好的稳定性的结果.     

行m-NSD随机变量阵列的完全收敛性

本文研究了行m-NSD随机变量阵列的完全收敛性问题.主要利用m-NSD随机变量的Kolmogorov型指数不等式,获得了行m-NSD随机变量阵列的完全收敛性定理,将Hu等（1998）andSung等（2005）的结果从独立情形推广到了m-NSD随机变量阵列.本文的结论同样推广了Chen等（2008）,Hu等（2009）,Qiu等（2011）和Wang等（2014）的结果.     

(α,δ)-弱刚性环上的Ore扩张

本文研究（α,δ）-弱刚性环上的Ore扩张环R[x;α,δ]的弱对称性、弱zip性、幂零p.p.性和幂零Baer性.利用对多项式的逐项分析的方法,证明了如果R是（α,δ）-弱刚性环和半交换环,则Ore扩张环R[x;α,δ]是弱对称的（弱zip的,幂零p.p.的,幂零Baer的）当且仅当R是弱对称的（弱zip的,幂零p.p.的,幂零Baer的）.这些结果统一和扩展了前面已有的相关结论.     

环Fp+vFp上互补对偶常循环码

本文研究了环F_p+vF_p上互补对偶（1-2v）-常循环码.利用环F_p+vF_p上（1-2v）-常循环码的分解式C=vC_1-v ⊕（1-v）C_v,得到了环F_p+vF_p上互补对偶（1-2v）-常循环码的生成多项式.然后借助从F_p+vF_p到F_p²的Gray映射,证明了环F_p+vF_p上互补对偶（1-2v）-常循环码的Gray像是F_p的互补对偶循环码.     

On two classes of finite supersoluble groups

Let ? be a complete set of Sylow subgroups of a finite group G, that is, a set composed of a Sylow p-subgroup of G for each p dividing the order of G. A subgroup H of G is called ?-S-semipermutable if H permutes with every Sylow p-subgroup of G in ? for all p?π(H); H is said to be ?-S-seminormal if it is normalized by every Sylow p-subgroup of G in ? for all p?π(H). The main aim of this paper is to characterize the ?-MS-groups, or groups G in which the maximal subgroups of every Sylow subgroup in ? are ?-S-semipermutable in G and the ?-MSN-groups, or groups in which the maximal subgroups of every Sylow subgroup in ? are ?-S-seminormal in G.     

Associativity of the <Emphasis Type="Italic">∇</Emphasis>-operation on bands in rings

Given a multiplicative band of idempotents S in a ring R, for all e,f∈S the ∇-product e ∇ f=e+f+fe−efe−fef is an idempotent that lies roughly above e and f in R just as ef and fe lie roughly below e and f. In this paper we study ∇-bands in rings, that is, bands in rings that are closed under ∇, giving various criteria for ∇ to be associative, thus making the band a skew lattice. We also consider when a given band S in R generates a ∇-band.     

Spanning trees with leaf distance at least four

For a graph G, we denote by i(G) the number of isolated vertices of G. We prove that for a connected graph G of order at least five, if i(G–S) < |S| for all ?? ≠ S ? V(G), then G has a spanning tree T such that the distance in T between any two leaves of T is at least four. This result was conjectured by Kaneko in “Spanning trees with constrains on the leaf degree”, Discrete Applied Math, 115 (2001), 73–76. Moreover, the condition in the result is sharp in a sense that the condition i(G–S) < |S| cannot be replaced by i(G–S) ≤ |S|. © 2006 Wiley Periodicals, Inc. J Graph Theory 55: 83–90, 2007     

The Distribution of Reciprocal Pairs Modulo Polynomials over a Finite Field

Given a finite field F_q of order q, a fixed polynomial g in –F_q[X] of positive degree, and two elements u and v in the ring of polynomials in R = F_q [X]/gF_q[X], the question arises: How many pairs (a, 6) are there in R × R so that ab ? 1 mod g and so that a is close to u while b is close to v ? The answer is, about as many as one would expect. That is, there are no favored regions in R × R where inverse pairs cluster. The error term is quite sharp in most cases, being comparable to what would happen with random distribution of pairs. The proof uses Kloosterman sums and counting arguments. The exceptional cases involve fields of characteristic 2 and composite values of g. Even then the error term obtained is nontrivial. There is no computational evidence that inverses are in fact less evenly distributed in this case, however.     

Gaussian Property of the Rings R(X) and R〈X〉

The content of a polynomial f over a commutative ring R is the ideal c(f) of R generated by the coefficients of f. A commutative ring R is said to be Gaussian if c(fg) = c(f)c(g) for every polynomials f and g in R[X]. A number of authors have formulated necessary and sufficient conditions for R(X) (respectively, R?X?) to be semihereditary, have weak global dimension at most one, be arithmetical, or be Prüfer. An open question raised by Glaz is to formulate necessary and sufficient conditions that R(X) (respectively, R?X?) have the Gaussian property. We give a necessary and sufficient condition for the rings R(X) and R?X? in terms of the ring R in case the square of the nilradical of R is zero.     

Some results on the achromatic number

Let G be a simple graph. The achromatic number ψ(G) is the largest number of colors possible in a proper vertex coloring of G in which each pair of colors is adjacent somewhere in G. For any positive integer m, let q(m) be the largest integer k such that ≤ m. We show that the problem of determining the achromatic number of a tree is NP-hard. We further prove that almost all trees T satisfy ψ (T) = q(m), where m is the number of edges in T. Lastly, for fixed d and ϵ > 0, we show that there is an integer N₀ = N₀(d, ϵ) such that if G is a graph with maximum degree at most d, and m ≥ N₀ edges, then (1 - ϵ)q(m) ≤ ψ (G) ≤ q(m). © 1997 John Wiley & Sons, Inc. J Graph Theory 26: 129–136, 1997     

A perturbative method for the spectral analysis of an acoustic multistratified strip

We consider the acoustic propagator A=−∇·c²∇ in the strip Ω={(x, z)∈ℝ²∣0<z<H} with finite width H>0. The celerity c depends for large ∣x∣ only on the variable z and describes the stratification of Ω: it is assumed to be in L^∞(Ω), bounded from below by c_min>0, such that there exists M>0 with c(x, z)=c₁(z) if x< −M and c(x, z)=c₂(z) if x>M. We look at the propagator A as a ‘perturbation’ of the free propagators A_j in Ω associated to the velocities c_j, j=1, 2, and implement a ‘perturbative’ method, adapting ideas of Majda and Vainberg. The spectrum of A is defined in section 2, a limiting absorption principle is proved in section 3 outside of a countable set Γ(A). The points of Γ(A) can only accumulate at the left of the thresholds of the free propagators. The needed material about A_j, j=1, 2, and some technical estimates for A are given in Appendix. © 1998 B. G. Teubner Stuttgart—John Wiley & Sons, Ltd.     

Similarity of operators associated with the Volterra relation

The “Volterra relation” is the commutation relation [S,V]⊂V ², where S is a not necessarily bounded operator, V is a bounded operator leaving D(S) invariant, and [⋅,⋅] is the Lie product. When S,V are so related, and in addition iS generates a bounded C ₀-group of operators and V has some general property, it is known that S+α V (α∈ℂ) is similar to S if and only if ℜ α=0 (cf. Theorem 11.17 in Kantorovitz, Spectral Theory of Banach Space Operators, Springer, Berlin, 1983). In particular, S−V is not similar to S. However, it is shown in this note that (without any restriction on V and on the group S(⋅) generated by iS), the perturbations (S−V)+P are similar to S for all P in the similarity sub-orbit {S(a)VS(−a);a∈ℝ} of V. When S is bounded, the above perturbations are similar to S for all P in the wider similarity sub-orbit {e ^aS Ve ^−aS ;a∈ℂ}.     

On the Cyclic Homology of an Algebra Associated with a Cyclic Quiver and a Monic Polynomial

In this article, we compute the Hochschild homology group of A = KΓ/(f(X ^s )), where KΓ is the path algebra of the cyclic quiver Γ with s vertices and s arrows over a commutative ring K, f(x) is a monic polynomial over K, and X is the sum of all arrows in KΓ. Moreover, we compute the cyclic homology group of A in the case f(x) = (x ? a) ^m , where a ∈ K, so that we can determine the cyclic homology of A in general when K is an algebraically closed field.