两个性质的完善与启示

文[2]在文[1]的基础上推出了如下两个性质： 性质1过双曲线x^2/a^2-y^2/b^2=1（a〉0,b〉0）的顶点A的弦AQ交于y轴于点R，过双曲线中心O的半弦OP∥AQ，则｜OP｜^2=1/2｜AR｜·｜AO｜．     

Precise Asymptotics in the Baum-Katz and Davis Laws of Large Numbers of ρ-mixing Sequences

Let {X,Xn;n ≥ 1} be a strictly stationary sequence of ρ-mixing random variables with mean zeros and finite variances. Set Sn =∑k=1^n Xk, Mn=maxk≤n｜Sk｜,n≥1.Suppose limn→∞ESn^2/n=：σ^2〉0 and ∑n^∞=1 ρ^2/d（2^n）〈∞,where d=2 if 1≤r〈2 and d〉r if r≥2.We prove that if E｜X｜^r 〈∞,for 1≤p〈2 and r〉p,then limε→0ε^2（r-p）/2-p ∑∞n=1 n^r/p-2 P{Mn≥εn^1/p}=2p/r-p ∑∞k=1（-1）^k/（2k＋1）^2（r-p）/（2-p）E｜Z｜^2（r-p）/2-p,where Z has a normal distribution with mean 0 and variance σ^2.     

Optimal integrability of some system of integral equations

We obtain the optimal integrability for positive solutions of the Euler-Lagrange system of the weighted Hardy-Littlewood-Sobolev inequality in R^n ：{u（x）=1/｜x｜^α｜∫R^n v（y）^q｜y｜^β｜x-y｜^λdy,v（x）=1/｜x｜^β∫R^n u（y）^p｜y｜^α｜x-y｜^λdy.C. Jin and C. Li [Calc. Var. Partial Differential Equations, 2006, 26： 447-457] developed some very interesting method for regularity lifting and obtained the optimal integrability for p, q 〉 1. Here, based on some new observations, we overcome the difficulty there, and derive the optimal integrability for the case of p, q ≥1 and pq ≠1. This integrability plays a key role in estimating the asymptotic behavior of positive solutions when ｜x｜ →0 and when ｜x｜→∞.     

椭圆的一个性质及应用

一、问题与探求 问题A,B是椭圆x^2/a^2＋y^2/b^2=1（a〉b〉0）上任意两点,O为坐标原点且∠AOB=90°,试判断1/｜OA｜^2＋1/｜OB｜^2是否为定值？     

A general result on precise asymptotics for linear processes of positively associated sequences

Let {εt; t ∈ Z^＋} be a strictly stationary sequence of associated random variables with mean zeros, let 0〈Eε1^2〈∞ and σ^2=Eε1^2＋1∑j=2^∞ Eε1εj with 0〈σ^2〈∞.{aj;j∈Z^＋} is a sequence of real numbers satisfying ∑j=0^∞｜aj｜〈∞.Define a linear process Xt=∑j=0^∞ ajεt-j,t≥1,and Sn=∑t=1^n Xt,n≥1.Assume that E｜ε1｜^2＋δ′〈 for some δ′〉0 and μ（n）=O（n^-ρ） for some ρ〉0.This paper achieves a general law of precise asymptotics for {Sn}.     

Positive Solutions for Singular Quasilinear Schrodinger Equations with One Parameter,II

We establish the existence of positive bound state solutions for the singular quasilinear Schrodinger equation iψ/t=-div（ρ（｜ψ｜^2） ψ）＋ω（｜ψ｜62）ψ-λρ（｜ψ｜^2）ψ,x∈Ω,t〉0,where ω（τ^2）τ→∞ as τ→ 0 and, λ 〉 0is a parameter and Ω is a ball in ^RN. This problem is studied in connection with the following quasilinear eigenvalue problem with Dirichlet boundary condition -div（ρ（｜ ψ｜^2） ψ）=λ1ρ（｜ψ｜^2）ψ=λ1ρ（｜ψ｜^2）ψ,x∈Ω.Indeed, we establish the existence of solutions for the above Schrodinger equation when A belongs to a certain neighborhood of the first eigenvahie λ1 of this eigenvalue problem. The main feature of this paper is that the nonlinearity ω｜ψ｜^2 is unbounded around the origin and also the presence of the second order nonlinear term. Our analysis shows the importance of the role played by the parameter A combined with the nonlinear nonhomogeneous term div （ρ（｜ ψ｜^2） ψ） which leads us to treat this prob- lem in an appropriate Orlicz space. The proofs are based on various techniques related to variational methods and implicit function theorem.     

向量的平方

对于向量的平方,我们有（1）^→2a=｜^→a｜^2;（2）（^→a＋^→b）^2=｜^→a｜^2＋｜^→b｜^2＋2｜^→a｜·｜^→b｜cosθ（θ为^→a与^→b的夹角）。向量的运算和其他运算一样,若能考虑到向量自身的平方,则往往可以收到事半功倍的效果．本文试举几例,以期引起重视．     

例谈单位向量的一张亮丽“名片”

《苏教版》必修四P64有这样一道习题：已知非零向量a,求向量1/（｜a｜）a的模.此题解决应该不难,可以很快求得｜1/（｜a｜）a｜=｜1/（｜a｜）｜·｜a｜=1,根据定义,发现1/（｜a｜）a其实是一个单位向量,而且由于音〉0,实际上1/（｜a｜）a表示的是与a同向的单位向量,     

广义Bochner-Riesz乘子的等价性及其应用——献给陆善镇教授75华诞

本文研究下面这两个函数,（1-｜x｜^ρ1）＋^α和（1-｜x｜^ρ2）＋^α,其中ρ1,ρ2和α均为正实数,文献上称这类函数为广义Bochner-Riesz乘子.本文将证明,当α给定时,对任意的ρ1〉0和ρ2〉0,这两个函数作为乘子,其乘子算子的L^p有界性和Hp有界性是等价的.     

有心曲线的一个美妙性质

我们在学习中发现了有心曲线的—个美妙性质： 性质1如图1，设P是椭圆x^2/a^＋y^2/b^2=1（a〉b〉0）上位于x轴上方的任意一点，A，B是椭圆的长轴端点，以AB为一边做矩形ABCD，｜AB｜=2a,｜AD｜=2b,PC交AB于E，PD交AB于F，则｜BE｜，｜EF｜，｜FA｜成等比数列。     

Binormal operator and *-Aluthge transformation

Let T = U｜T｜ be the polar decomposition of a bounded linear operator T on a Hilbert space. The transformation T = ｜T｜^1/2 U｜T｜^1/2 is called the Aluthge transformation and Tn means the n-th Aluthge transformation. Similarly, the transformation T（＊）=｜T＊｜^1/2 U｜T＊｜＆1/2 is called the ＊-Aluthge transformation and Tn^（＊） means the n-th ＊-Aluthge transformation. In this paper, firstly, we show that T（＊） = UV｜T^（＊）｜ is the polar decomposition of T（＊）, where ｜T｜^1/2 ｜T^＊｜^1/2 = V｜｜T｜^1/2 ｜T^＊｜^1/2｜ is the polar decomposition. Secondly, we show that T（＊） = U｜T^（＊）｜ if and only if T is binormal, i.e., [｜T｜, ｜T^＊｜]=0, where [A, B] = AB - BA for any operator A and B. Lastly, we show that Tn^（＊） is binormal for all non-negative integer n if and only if T is centered, and so on.     

Normal Functions Concerning Shared Values

In this paper we discuss normal functions concerning shared values. We obtain the follow result. Let F be a family of meromorphic functions in the unit disc A, and a be a nonzero finite complex number. If for any f ∈F, the zeros of f are of multiplicity, f and f′ share a, then there exists a positive number M such that for any f∈F1（1-｜z｜^2） ｜f′（z）｜/1＋｜f（z）｜^2≤M.     

一个非等价转化问题的探究

某资料上有这样一个问题： 问题｜2x-a｜＋x^-2≥1对任意x〉0都成立,求a的取值范围。 给出的解法是：     

一个关于上凸密度猜测的否定回答

Let E be a self-similar set satisfying the open set condition. Professor Xu conjectures in his doctoral degree thesis that if H^8（E） 〈｜E｜^8, then for any x ∈ E, the inequality ^-D^3C（E,x）〉H^8（E）/｜E｜^8holds, where 3 = dimH（E）. The above conjecture is negatively answered in this＇paper.     

一个恒成立问题的正误辨析

1．提出问题 例题 已知不等式｜a＋2x｜〉x-1,对x∈[0,2]恒成立,求a的取值范围。 解法一 原不等式化为a-2x〉x-1或a-2x〈1-x,即a〉3x-1或a〈1＋32。     

Hardy-Sobolev类上的Bohr型不等式

Let β 〉 0 and Sβ ：= {z ∈ C ： ｜Imz｜ 〈β} be a strip in the complex plane. For an integer r ≥ 0, let H∞^Г,β denote those real-valued functions f on R, which are analytic in Sβ and satisfy the restriction ｜f^（r）（z）｜ ≤ 1, z ∈ Sβ. For σ 〉 0, denote by Bσ the class of functions f which have spectra in （-2πσ, 2πσ）. And let Bσ^⊥ be the class of functions f which have no spectrum in （-2πσ, 2πσ）. We prove an inequality of Bohr type
‖f‖∞≤π/√λ∧σ^r∑k=0^∞（-1）^k（r＋1）/（2k＋1）^rsinh（（2k＋1）2σβ）,f∈H∞^r,β∩B1/σ,
where λ∈（0,1）,∧and ∧′are the complete elliptic integrals of the first kind for the moduli λ and λ′=√1- λ^2,respectively,and λ satisfies
4∧β/π∧′=1/σ.
The constant in the above inequality is exact.     

向量数量积的新几何意义及应用

我们知道,向量a与b的数量积为a·b=｜a｜·｜b｜cos〈a,b〉,其中涉及三个量.换个角度看,可以关注两个量：｜a｜与｜b｜cos〈a,b〉,其中｜b｜cos〈a,b〉表示向量b在向量a方向上的投影,利用这个几何意义可降维（将二维平面内的问题转化到一维直线上）,方便地求两向量的数量积.然而从形上看,还需判断投影的正负,“形”还不够到位.能否找到更为直接的几何意义呢？从图形上看,两向量构成一个三角形,     

关于Campanato空间的一个注记

类似于Campanato空间理论，本文对具有以下连续模的函数类给出了一局部积分刻画：｜u（x）-u（y）｜≤C｜x—y｜^α（log｜x—y｜^-1）β，z，y∈Ω，其中C〉0，Ω为R^d中一正则区域，α∈（0，1]，β∈[0，1]．     

从一个双曲线焦半径错题说起

在一份全国重点中学高考调研试卷中有这样一道题：已知双曲线：x^2/a^2-y^2/b^2=1（a〉0,b〉0），F是其左焦点，过F作直线交双曲线于A。B两点，设｜AF｜—m，｜FB｜=n,则1/m＋1/n的值为——。     

无界域上带Hardy项和临界非线性项的半线性椭圆问题的全局紧性结果

本文讨论了下面一类带,Hardy项和临界非线性项的半线性椭圆问题：{-△u-μ u/｜x｜^2＋a（x）u=｜u｜^2^＊-2 u＋k（x）｜u｜^q-2u,u∈H^1（R^N）（＊）的全局紧性结果及其正解的存在性,其中2^＊=2N／（N-2）是临界的Sobolev指标,2〈q〈2^＊,0≤μ〈μ^-△=（N-2）^2／4,a（x）,k（x）∈C（R^N）．通过对问题（＊）所对应的能量泛函进行紧性分析,在a（x）和k（x）满足一定条件下,得到了此问题正解的存在性．