Mbius反演与高维算术Fourier变换

将 M bius反演公式推广到一般的惟一分解半群上 ,在建立了 n维整点与 n次代数整数环的环同构的基础上利用广义函数得到了高维 Fourier系数与M bius函数之间的一般关系 .它是一维算术 Fourier变换 (Arithmetic FourierTransform简称 AFT)在高维的自然推广 .     

不可分的正定幺模Hermite型的构作

本文给出了构作Z[m^1/2i]上不可分的正定幺模n秩Hermite格当m?3(mod4)时的方法.对任何自然数n,除了n=2,3,4,5(n=2,3)的例外情形,证明了存在Gauss整环Z[i](整环Z[2^1/2i])上不可分的正定幺模n秩正规Hermi-te格并给出它们的明显结构.又对任何n=4k(n=2k)构作了Z[i][(Z2^1/2i])上不可分的正定幺模n秩偶Hermite格.     

广义M(o|¨)bius变换和算术Fourier变换

离散Fourier变换(DFT)在数字信号处理等许多领域中占有重要地位.近年来,出现一种优于FFT的算术Fourier变换来计算DFT.在广义Mobius变换的基础上,本文采用了一种改进的AFT来计算DFT,这种方法可以直接提取DFT的系数,且用数论的方法阐明了这一过程,并展开了进一步的讨论.这也代表了数论方法应用在计算数学领域的一个新的发展方向.     

广义Moebius变换和算术Fourier变换

离散Fourier变换(DFT)在数字信号处理等许多领域中占有重要地位．近年来，出现一种优于FFT的算术Fourier变换来计算DFT．在广义Moebius变换的基础上，本文采用了一种改进的AFT来计算DFT，这种方法可以直接提取DFT的系数，且用数论的方法阐明了这一过程，并展开了进一步的讨论．这也代表了数论方法应用在计算数学领域的一个新的发展方向．     

广义M(o)bius变换和算术Fourier变换

离散Fourier变换(DFT)在数字信号处理等许多领域中占有重要地位.近年来,出现一种优于FFT的算术Fourier变换来计算DFT.在广义M(o)bius变换的基础上,本文采用了一种改进的AFT来计算DFT,这种方法可以直接提取DFT的系数,且用数论的方法阐明了这一过程,并展开了进一步的讨论.这也代表了数论方法应用在计算数学领域的一个新的发展方向.     

主理想整环上的线性方程组的通解

将文[1]中整数环上的线性方程组问题推广到主理想整环上,利用主理想整环上的矩阵的初等变换及等价标准形导出了主理想整环上的线性方程组有解的一个充分必要条件和求解方法.最后,通过实例说明了算法.     

紧致Lie群上Fourier级数的Salem型定理

本文从一维环群上Salem条件的一个等价形式出发,在紧致Lie群上建立了函数的Salem条件,从而把一维Fourier级数的 Salem定理推广到紧 Lie群上。在紧 Abel Lie群上,利用一个简单的引理,本文还改进了多重Fourier级数的Salem定理。     

Dirichlet characters,Gauss sums and arithmetic Fourier transforms

In this paper, a general algorithm for the computation of the Fourier coefficients of 2π-periodic(continuous) functions is developed based on Dirichlet characters, Gauss sums and the generalized M¨obius transform. It permits the direct extraction of the Fourier cosine and sine coefficients. Three special cases of our algorithm are presented. A VLSI architecture is presented and the error estimates are given.     

FOURIER 分析在微波天线中的一点初步运用

我们应用 Fourier 分析,证明了微波天线方向图的两个基本性质,分析了一类整函数的零点分布,提出了几个尚待解决的实际问题.一、实际意义在有限区间上的 Fourier 变换是有实际意义的.我们考查一个直径为 D 的微波线形天线 A.(见图1)在天线 A 上,振     

关于Euler数一个猜想的证明

研究Euler数的猜想:对于任何素数p≡1 mod4,E(p-1)／20 mod p．根据Euler数本身的性质和Fourier级数对于Gauss和的应用,证明了这个猜想是成立的．     

Heat kernel for the elliptic system of linear elasticity with boundary conditions

We consider the elliptic system of linear elasticity with bounded measurable coefficients in a domain where the second Korn inequality holds. We construct heat kernel of the system subject to Dirichlet, Neumann, or mixed boundary condition under the assumption that weak solutions of the elliptic system are Hölder continuous in the interior. Moreover, we show that if weak solutions of the mixed problem are Hölder continuous up to the boundary, then the corresponding heat kernel has a Gaussian bound. In particular, if the domain is a two dimensional Lipschitz domain satisfying a corkscrew or non-tangential accessibility condition on the set where we specify Dirichlet boundary condition, then we show that the heat kernel has a Gaussian bound. As an application, we construct Green's function for elliptic mixed problem in such a domain.     

On renormalizing Gaussian fields

Summary We investigate the Gaussian self-similar fields and their Gaussian domain of attraction. Both discrete and generalized fields are considered.     

Local asymptotic mixed normality of transformed Gaussian models for random fields

Local asymptotic mixed normality (LAMN) of a class of transformed Gaussian models for discretely observed random fields is proved. The original Gaussian random field is assumed to be the product of a deterministic process and a process with independent increments. The transformed process is observed only on discrete lattice points in the unit cube and fixed domain asymptotics is investigated. This model is useful for modeling random fields with non-Gaussian marginal distributions.     

The Gaussian free field and Hadamard’s variational formula

We relate the Gaussian free field on a planar domain to the variational formula of Hadamard which explains the change of the Green function under a perturbation of the domain. This is accomplished by means of a natural integral operator—called the Hadamard operator—associated with a given flow of growing domains.     

Computation of paraxial wave fields using transparent boundary conditions

The parabolic wave equation is solved numerically by applying transparent conditions used to confine the computational domain. A numerical implementation of the boundary conditions is proposed based on representing the incident wave as a superposition of Gaussian beams. A modification of the transparent conditions in the case of dielectric objects extending beyond the computational domain is described. Numerical examples are presented.     

A note on multivariate Gaussian estimates

An upper bound of multivariate Gaussian probability for a general convex domain D is given based on a geometric observation. The bound is sharper than known ones on multivariate Mills' ratio in many cases.     

Extremes of projections of functional time series on data–driven basis systems

The paper is concerned with the extreme behavior of projections of time series of functions onto data-driven basis systems, for example, on the estimated functional principal components. The coefficients of these projections, called the scores, encode the shapes of the curves. Within the framework of functional data analysis, the extreme shapes are those corresponding to multivariate extremes of the scores. The scores are not directly observable, and must be computed from the data. Even for iid Gaussian functions, they form a triangular array of dependent non–Gaussian vectors. Thus, even though the extreme behavior of the population scores of Gaussian functions follows from well–known results, it is not clear what the extreme behavior of their approximations computed from the data is. We clarify these issues for Gaussian functions and for more general functional time series whose projections are in the Gumbel domain of attraction.     

The asymptotic distribution of the maxima of a Gaussian random field on a lattice

Under mild conditions on the covariance function of a stationary Gaussian process, the maxima behaves asymptotically the same as the maxima of independent, identically distributed Gaussian random variables. In order to achieve extremal clustering, Hsing et al. (Ann Appl Probab 6:671–686, 1996) considered a triangular array of Gaussian sequences in which the correlation between “neighboring” observations approaches 1 at a certain rate. Using analogues of the conditions of Hsing et al., which allows for strong local dependence among variables but asymptotic independence, it is possible to show that two-dimensional Gaussian random fields also exhibit extremal clustering in the limit. A closed form expression for the extremal index governing the clustering will be provided. The results apply to Gaussian random fields in which the spatial domain is rescaled.     

Maslov complex germ and high-frequency Gaussian beams for cold plasma in a toroidal domain

Asymptotic vector solutions describing, in the linear approximation, the passage of high-frequency Gaussian beams through an electroneutral plasma occupying a toroidal domain T (modeling a tokamak chamber) are constructed in a fairly effective form by using the Maslov complex germ theory. The particle density and the magnetic field in T are assumed to be given. Based on Radon transforms, the reconstruction of the particle density and the magnetic field from measurements of the characteristics of Gaussian beams after their passage through T is discussed.     

Remarks on analytic smoothing effect for the Schrödinger equation

We study analytic smoothing effect of solutions to the Schrödinger equation with Cauchy data decaying exponentially at infinity. The domain of analyticity in the space variables of solutions is described under weight conditions on the data in terms of the corresponding supporting function. The domain of analyticity in the time variable is characterized by means of weight conditions of Gaussian type on the data. A generalization of various isometrical identities related to the analytic smoothing effect is introduced.