pp 151-166 May 2013
Bell Numbers, Determinants and Series
In this article, we study Bell numbers and Uppuluri Carpenter numbers. We obtain various expressions and relations between them. These include polynomial recurrences and expressions as determinants of certain matrices of binomial coefficients.
pp 167-175 May 2013
The Smallest Randić Index for Trees
The general Randic index Rα(G) is the sum of the weight d(u)d(v)α over all edges uv of a graph G, where α is a real number and d(u) is the degree of the vertex u of G. In this paper, for any real number α=0, the first three minimum general Randic indices among trees are determined, and the corresponding extremal trees are characterized.
pp 177-192 May 2013
A New Generalization of Hardy-Berndt Sums
Muhammet Cihat Dağli Mümün Can
In this paper, we construct a new generalization of Hardy–Berndt sums which are explicit extensions of Hardy–Berndt sums. We express these sums in terms of Dedekind sums $s_r(h,k:x,y|\lambda)$ with $x=y=0$ and obtain corresponding reciprocity formulas.
pp 193-201 May 2013
On Partial Sums of a Spectral Analogue of the Möbius Function
Kalyan Chakraborty Makoto Minamide
Sankaranarayanan and Sengupta introduced the function $\mu^∗(n)$ corresponding to the Möbius function. This is defined by the coefficients of the Dirichlet series $1/L_f(s)$, where $L_f(s)$ denotes the 𝐿-function attached to an even Maaß cusp form 𝑓. We will examine partial sums of $\mu^∗(n)$. The main result is $\Sigma_{n\leq x}\mu^∗(n)=O(x \exp(-A\sqrt{\log x}))$, where 𝐴 is a positive constant. It seems to be the corresponding prime number theorem.
pp 203-211 May 2013
Distribution of Residues and Primitive Roots
Given an integer $N\geq 3$, we shall prove that for all primes $p\geq(N-2)^2 4^N$, there exists 𝑥 in $(\mathbb{Z}/p\mathbb{Z})^∗$ such that $x,x+1,\ldots,x+N-1$ are all squares (respectively, non-squares) modulo 𝑝. Similarly, for an integer $N\geq 2$, we prove that for all primes $p\geq \exp(2^{5.54N})$, there exists an element $x\in(\mathbb{Z}/p\mathbb{Z})^∗$ such that $x,x+1,\ldots,x+N-1$ are all generators of $(\mathbb{Z}/p\mathbb{Z})^∗$.
pp 213-223 May 2013
On Rationality of Moduli Spaces of Vector Bundles on Real Hirzebruch Surfaces
Indranil Biswas Ronnie Sebastian
Let 𝑋 be a real form of a Hirzebruch surface. Let $M_H(r,c_1,c_2)$ be the moduli space of vector bundles on 𝑋. Under some numerical conditions on $r,c_1$ and $c_2$, we identify those $M_H(r,c_1,c_2)$ that are rational.
pp 225-233 May 2013
Characteristic Classes for $GO(2n)$ in étale Cohomology
Let $GO(2n)$ be the general orthogonal group (the group of similitudes) over any algebraically closed field of characteristic $\neq 2$. We determine the smooth-étale cohomology ring with $\mathbb{F}_2$ coefficients of the algebraic stack $BGO(2n)$. In the topological category, Holla and Nitsure determined the singular cohomology ring of the classifying space $BGO(2n)$ of the complex Lie group $GO(2n)$ in terms of explicit generators and relations. We extend their results to the algebraic category. The chief ingredients in this are: (i) an extension to étale cohomology of an idea of Totaro, originally used in the context of Chow groups, which allows us to approximate the classifying stack by quasi projective schemes; and (ii) construction of a Gysin sequence for the $\mathbb{G}_m$-fibration $BO(2n)\to BGO(2n)$ of algebraic stacks.
pp 235-238 May 2013
A Note on 2-Nilpotence of Finite Groups
Ballester-Bolinches and Guo showed that a finite group 𝐺 is 2-nilpotent if 𝐺 satisfies: (1) a Sylow 2-subgroup 𝑃 of 𝐺 is quaternion-free and (2) $\Omega_1(P\cap G')\leq Z(P)$ and $N_G(P)$ is 2-nilpotent. In this paper, it is obtained that 𝐺 is a non-2-nilpotent group of order $16q$ for an odd prime 𝑞 satisfying (1) a Sylow 2-subgroup 𝑃 of 𝐺 is not quaternion-free and (2) $\Omega_1(P\cap G')\leq Z(P)$ and $N_G(P)$ is 2-nilpotent if and only if $q=3$ and $G\cong GL_2(3)$.
pp 239-244 May 2013
Conjugacy Class Sizes and Solvability of Finite Groups
Let 𝐺 be a finite group and $G^∗$ be the set of primary, biprimary and triprimary elements of 𝐺. We prove that if the conjugacy class sizes of $G^∗$ are $\{1,m,n,mn\}$ with positive coprime integers 𝑚 and 𝑛,then 𝐺 is solvable. This extends a recent result of Kong (Manatsh. Math. 168(2)(2012) 267–271).
pp 245-251 May 2013
Notes on Discrete Subgroups of Möbius Transformations
Hua Wang Yueping Jiang Wensheng Cao
Jørgensen’s inequality gives a necessary condition for a nonelementary two generator subgroup of $SL(2,\mathbb{C})$ to be discrete. By embedding $SL(2,\mathbb{C})$ into $Û(1,1;\mathbb{H})$, we obtain a new type of Jørgensen’s inequality, which is in terms of the coefficients of involved isometries. We provide an example to show that this result gives an improvement over the classical Jørgensen’s inequality.
pp 253-256 May 2013
A Note on the Fuglede-Putnam Theorem
We prove the following generalization of the Fuglede–Puntam theorem. Let 𝑁 be an unbounded normal operator in the Hilbert space, and let 𝐴 be an unbounded self-adjoint operator such that $D(N)\subseteq D(A)$. Then, $AN\subseteq N^∗A\Rightarrow AN^∗\subseteq NA$.
pp 257-281 May 2013
Multiple Decomposability of Probabilities on Contractible Locally Compact Groups
Operator decomposable probabilities on vector spaces – generalizing (semi-)stable and self-decomposable laws – are well known. Here we are concerned with multiple decomposability on locally compact groups. In fact, as it turned out that contraction properties play an essential role, throughout we concentrate on contractible locally compact groups.
pp 283-292 May 2013
Asymptotic Distribution of Products of Sums of Independent Random Variables
Yanling Wang Suxia Yao Hongxia Du
In the paper we consider the asymptotic distribution of products of weighted sums of independent random variables.
pp 293-302 May 2013
We generalize Tollmien’s solutions of the Rayleigh problem of hydrodynamic stability to the case of arbitrary channel cross sections, known as the extended Rayleigh problem. We prove the existence of a neutrally stable eigensolution with wave number $k_s>0$; it is also shown that instability is possible only for $0 < k < k_s$ and not for $k>k_s$. Then we generalize the Tollmien–Lin perturbation formula for the behavior of $c_i$, the imaginary part of the phase velocity as the wave number $k\to k_s$ − to the extended Rayleigh problem and subsequently, we use this formula to demonstrate the instability of a particular shear flow.
Current Issue
Volume 129 | Issue 2
April 2019
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