群代数作用遍历性的一点注记

证明了由自由群整数环上一类元素确定的代数作用的遍历性,计算了Heisenberg群因子中特定元素的Fuglede-Kadison行列式值.     

广义范德蒙行列式

把n阶范德蒙行列式D中任一行(设为第i行)上元素的幂指数一般化,换成任意的整数k(正,零或负),这样得到的行列式与三个参数有关:阶数n,行数i,指数k.它既包含了原来的行列式D,又涵盖了其他许多不同的行列式.本文对指数k的不同情形分别进行讨论,并以D与D第二行元素的初等对称多项式分别表示出k≥n与k0时行列式之值.     

多维特征函数的解析性质及其分布的尾性状

设X为d维(d≥2)随机向量,本文获得了X的分布函数的非整数阶矩及奇数阶矩存在的充分必要条件。同时还研究了X的尾概率下降速度与其相应特征函数解析性质之间的关系,推广了Csrg的结果以及解决了他在文献[3]中提出的问题。     

构造奇次同心幻方的一种方法

幻方是古老的数学游戏,经过几个世纪的发展形成了很多有趣的构造方法.利用行列式的性质和变换得到了构造奇数阶同心幻方原基的一种方法,利用这种方法和排列组合都能得到任意奇数阶幻方的多种形式.     

初一数学竞赛训练题(五)

一、选择题 1.若abC>0,则|a|/a |b|/b |c|/c-|abc|/abc的值为( ) (A)2 (B)-2 (C)±2 (D)以上都不对 2.已知n是偶数,m是奇数,方程组:是整数、那么( ) (A)P、q都是偶数 (B)p、q都是奇数 (C)p是奇数,q是偶数 (D)p是偶数,q是奇数 3.设a、b都是整数。 (1)若a 5b是偶数,则a-3b也是偶数 (2)若a b能被3整除,则a、b都能被3整除     

美国Putnam数学竞赛中两道行列式证明题的泰勒公式解法

介绍了美国Putnam数学竞赛中两道行列式证明题的分析证明方法.选取行列式中的某个参数(常数)为变量,使得行列式可设为该变量的多项式,然后分别计算函数值和各阶导数值,进而利用泰勒展式即可计算出行列式的值.     

整数计分投票方法下全排序概率问题研究

讨论了在与Borda投票规则相似的整数计分投票方法中,投票结果使备选方案集产生全排序(任意两个备选方案的总分值不同)的概率P的问题.给出了在一定假设条件下计算P值的相关公式;通过分析运行计算机程序得到的数据,讨论了P值关于整数计分投票问题的三个变量的单调性性质;最后根据P值函数的单调性性质,指出应如何设计和调整整数计分投票规则.     

值为恒值的行列式

在[1]文中介绍了由组合数排列成的一类带1行列式其值恒等于1。本文推广了这个结果,给出几类新的值为恒值的行列式,由此揭示[1]文中行列式的实质。     

北京数学奥林匹克学校课堂实录

钻畏题 或毛用居卜省民 学期 反证法 初中三年级 2004一2005 学年度第二学期 训练目的 昧求 =l数 …粤一牌二为整数滋x=0:二- 二次函数y一a扩+bx+。的值都是奇 证:二次方程a扩+bx+。~O没有整数根. 一’证明士一。时,1夕一仑为奇数; x二l时,四于只十b七今为奇数,、 a十b为偶数.。、、州- 若a扩+bx+‘~O有整数根x。,则有 ax。2+bx。+c=0, (呼+b)x。’一b二。’+bx。+犷。; 添呱二缨鄂罐 巍蘸蘸蘸蘸蘸蘸蘸蘸蘸蘸潺 缪嘛狐赢 纂蘸薰矍翼 随堂测试 .证明:涯是无理数. 学生课后练习 1.已知自然数a、b、‘的公约数为1, 且az+夕~产,求证:‘必为奇数…     

整数的平方的一些性质

在国内外的数学竞赛题中,有一些题目的解法实际上只用到了整数的平方的某些性质,所涉及的知识是相当少的;但是,对于不习惯于利用这些性质的人,又会感到这些题目有一定的难度。本文打算通过一些例子,向中学生介绍这方面的解题方法。一、大家知道,所有的整数可以分为偶数和奇数两大类。偶数能表为2k的形式,奇数能表为2k 1的形式,这里k是整数。先看偶数的平方,由于(2k)~2=4k~2,可见任何偶数的平方能被4整除。再看奇数的平方,(2k 1)~2=4k~2 4k 1=4k~2(k 1) 1,由于k与k 1是相邻的两整数,故其中恰有一偶数,因此4k(k 1)能被     

Exact asymptotics of the characteristic polynomial of the symmetric Pascal matrix

We have obtained the exact asymptotics of the determinant . Inverse symbolic computing methods were used to obtain exact analytical expressions for all terms up to relative order L⁻¹⁴ to the leading term. This determinant is known to give weighted enumerations of cyclically symmetric plane partitions, weighted enumerations of certain families of vicious walkers and it has been conjectured to be proportional to the one point function of the O(1) loop model on a cylinder of circumference L. We apply our result to the loop model and give exact expressions for the asymptotics of the average of the number of loops surrounding a point and the fluctuation in this number. For the related bond percolation model at the critical point, we give exact expressions for the asymptotics of the probability that a point is on a cluster that wraps around a cylinder of even circumference and the probability that a point is on a cluster spanning a cylinder of odd circumference.     

Stability of Picard bundle over moduli space of stable vector bundles of rank two over a curve

Answering a question of [BV] it is proved that the Picard bundle on the moduli space of stable vector bundles of rank two, on a Riemann surface of genus at least three, with fixed determinant of odd degree is stable.     

On primitively universal quadratic forms

In 1999, Manjul Bhargava proved the Fifteen Theorem and showed that there are exactly 204 universal positive definite integral quaternary quadratic forms. We consider primitive representations of quadratic forms and investigate a primitive counterpart to the Fifteen Theorem. In particular, we give an efficient method for deciding whether a positive definite integral quadratic form in four or more variables with odd square-free determinant is almost primitively universal.     

Spherically Symmetric Logistic Distribution

In this paper exact formulae of the probability density function for the spherically symmetric distribution with marginal logistic are given. They are entirely different for odd and even dimensions. For an odd number of dimensions it is possible to express them by elementary functions but for an even number of dimensions, it is possible only by an infinite series of functions. These series, however, are very convenient for computations and could be useful in practice.     

Cyclic automorphisms of a countable graph and random sum-free sets

Cyclic automorphisms of the countable universal ultrahomogeneous graph are investigated using methods of Baire category and measure theory. This leads to the study of random sumfree sets; it is shown that the probability that such a set consists entirely of odd numbers is strictly positive, and bounds are given.     

A Prime Sensitive Hankel Determinant of Jacobi Symbol Enumerators

We show that the determinant of a Hankel matrix of odd dimension n whose entries are the enumerators of the Jacobi symbols which depend on the row and the column indices vanishes if and only if n is composite. If the dimension is a prime p, then the determinant evaluates to a polynomial of degree p − 1 which is the product of a power of p and the generating polynomial of the partial sums of Legendre symbols. The sign of the determinant is determined by the quadratic character of −1 modulo p. The proof of the evaluation makes use of elementary properties of Legendre symbols, quadratic Gauss sums, and orthogonality of trigonometric functions.     

On a bilateral birth-death process with alternating rates

We consider a bilateral birth-death process characterized by a constant transition rate ?? from even states and a possibly different transition rate??? from odd states. We determine the probability generating functions of the even and odd states, the transition probabilities, mean and variance of the process for arbitrary initial state. Some features of the birth-death process confined to the non-negative integers by a reflecting boundary in the zero-state are also analyzed. In particular, making use of a Laplace transform approach we obtain a series form of the transition probability from state 1 to the zero-state.     

Examples of Fano varieties of index one that are not birationally rigid

A conjecture of Pukhlikov states that a smooth Fano variety of dimension at least 4 and index one is birationally rigid. We show that a general member of the linear system given by the ample generator of the Picard group of the moduli space of stable, rank 2 bundles with fixed determinant of odd degree on a curve of genus at least 3 is not birationally rigid.

     

On similarity classes of second order matrices with zero trace over the ring of integers

In this paper we consider the problem of similarity of matrices over integers and describe canonical representatives of the similarity classes of 2 × 2 matrices with zero trace and determinant equal an odd power of a prime number.