CRW型交换子在Triebel-Lizorkin空间的有界性

本文考虑交换子[b,T]在Triebel-Lizorkin空间上的有界性,其中b∈BMO(Rn),T是卷积型奇异积分算子,其核为Ω∈Llog+L(Sn-1),给出了该交换子在Fs,qp(Rn)(s＞0,1＜p,q＜∞)上有界的一个等价条件.     

Marcinkiewicz积分交换子在Herz型空间中的弱型估计

用μΩ表示Marcinkiewicz积分,μΩ,b表示μΩ与函数b∈BMO(R~n)生成的交换子．本文证明了交换子μΩ,b是从Herz型Hardy空间H■_q~(n(1-(1/q)),p)(R~n)到弱Herz空间W■_q~(n(1-(1/q)),p)(R~n)有界的,其中0＜p≤1,1＜q＜∞．     

Marcinkiewicz积分交换子在一些Hardy空间的有界性

讨论了由核函数满足具有某类Dini条件的Marcinkiewicz积分μΩ及函数b∈Lipβ(R~n)生成的交换子μ(_Ω,b)~m的性质.证明了Marcinkiewicz积分交换子μ_(_Ω,b)~m在Hardy型空间H_(bm,s)(R~n)上有界,也在Herz型Hardy空间H_(bm)K_p~(a_q)(R~n)上有界.     

带参数的Littlewood-Paley g_λ~*函数的交换子在Morrey空间上的紧性

本文给出了交换子[b,g_λ~(*,ρ)]在Morrey空间L~(p,α)(R~n)上的紧性特征,其中1p∞,0αn.更精确地说,证明了交换子[b,g_λ~(*,ρ)]是Morrey空间上紧算子的充要条件是b∈VMO(R~n),其中g_λ~(*,ρ)表示带参数的Littlewood-Paley g_λ~*函数.     

双线性Fourier乘子交换子的有界性与紧性

假定T_σ是关于乘子σ的双线性Fourier乘子算子,其中σ满足如下Sobolev正则条件:对某个s∈(n,2n],有sup_(κ∈Z)‖σ_k‖W~s(R~(2m))∞.对于p_1,p_2,p∈(1,∞)且满足1/p=1/p_1+1/p_2和ω=(ω_1,ω_2)∈A_(p/t)(R~(2n)),建立了T_σ及其与函数b=(b_1,b_2)∈(BMO(R~n))~2生成的交换子T_(σ,b)由L~(p_1,λ)(ω_1)×L~(p_2,λ)(ω_2)到L~(p,λ)(v_w)的有界性;同时,在b_1,b_2∈CMO(R~n)(C_c~∞(R~n)在BMO拓扑下的闭包)的条件下,证明交换子T_(σ,b)是L~(p_1,λ)(ω_1)×L~(p_2,λ)(ω_2)到L~(p,λ)(v_w)的紧算子.为了得到主要结果,我们先后建立了几个双(次)线性极大函数在加多权Morrey空间上的有界性以及该空间中准紧集的判定.     

带粗糙核的参数型Marcinkiwicz积分交换子在齐次Morrey-Herz空间上的有界性

本文研究一类带粗糙核的参数型Marcinkiwicz积分算子与BMO(R~n)函数生成的交换子μ_(?,b)~ρ在齐次Morrey-Herz空间MK˙_(p,q)~(α,λ)(R~n)上的有界性,利用经典调和分析的方法和实变技巧,证明了μ_(?,b)~ρ是从MK˙_(p,q)~(α,λ)(R~n)到MK˙_(p,q)~(α,λ)(R~n)上有界的.     

分数次积分交换子的紧致性

考虑分数次积分算子I_α和乘法算子B的交换子[I_α,B],我们证明,当b∈CMO时,[I_α,B]是映L~p (R~n)到L~q(R~n)的紧算子,反之,如b∈BMO且[I_α,B]是映L~p(R~n)到L~q(R~n)的紧算子,那么b∈CMO,这里p,q满足一定要求。     

与非光滑核的奇异积分算子的Toeplitz算子的λ-中心BMO估计

设L是L~2(R~n)上的一个解析半群的无穷小生成元,核函数满足高斯上界.L~(-α/2)(0αn)是由L生成的广义分数次积分算子,若T_(j,1)是与L有关的带有非光滑核的奇异积分算子,或T_(j,1)=I,T_(j,2),T_(j,4)是线性算子且具有(B~(p,λ),B~(p,λ))有界性(1p∞,λ∈R),T_(j,3)=±I(j=1,2,…,m),其中I为恒等算子,M_b是乘法算子.当b∈CBMO~(p_2,λ_2)函数时,证明Toeplitz型算子θ_a~b是B~(p_1,λ_1)到B~(q,λ)上的有界算子,并由此得广义分数次积分交换子[b,L~(-a/2)]和非光滑核的奇异积分交换子[b,T]在中心Morrey型空间上的有界性.     

双线性分数次积分算子交换子在Morrey空间上有界的充分必要条件

In this paper,we obtain that b∈ BMO(R~n) if and only if the commutator[b,I_α]is bounded from the Morrey spaces L~(p_1,λ_1)(R~n)×L~(p_2,λ_2)(R~n) to L~(q,λ)(R~n),for some appropriate indices p,q,λ,μ.Also we show that b ∈ Lip_β(R~n) if and only if the commutator[b,I_α]is bounded from the Morrey spaces L~(p_1,λ_1)(R~n)×L~(p_2,λ_2)(R~n) to L~(q,λ)(R~n),for some appropriate indices p,q,λ,μ.     

一类Marcinkiewicz积分交换子的端点估计

本文得到Ω满足Dini型条件时,Marcinkiewicz积分交换子μΩ,b(f)的端点估计:|{x∈R~n:μΩ,b(f)(x)＞λ}|≤c‖b‖BMO∫_(R~n)(|f(x)|)/λ(1+log+(|f(x)|)/λ)dx．     

RECENT PROGRESS ON SPHERICAL HARMONIC APPROXIMATION MADE BY BNU RESEARCH GROUP ——In memory of Professor Sun Yongsheng

As early as in 1990, Professor Sun Yongsheng, suggested his students at Beijing Normal University to consider research problems on the unit sphere. Under his guidance and encouragement his students started the research on spherical harmonic analysis and approximation. In this paper, we incompletely introduce the main achievements in this area obtained by our group and relative researchers during recent 5 years （2001-2005）. The main topics are： convergence of Cesaro summability, a.e. and strong summability of Fourier-Laplace series; smoothness and K-functionals; Kolmogorov and linear widths.     

A unified approach to certain problems of best local approximation

In this paper we study best local quasi-rational approximation and best local approximation from finite dimensional subspaces of vectorial functions of several variables. Our approach extends and unifies several problems concerning best local multi-point approximation in different norms.     

Boundedness for commutators of multipliers on Hardy type spaces

In this paper, we study the commutators generalized by multipliers and a BMO function. Under some assumptions, we establish its boundedness properties from certain atomic Hardy space Hb^p（R^n） into the Lebesgue space L^p with p 〈 1.     

THE 8~(th) INTERNATIONAL CONGRESS ON INDUSTRIAL AND APPLIED MATHEMATICS

<正>August 10-14,2015Beijing,ChinaThe International Congress on Industrial and Applied Mathematics(ICIAM)is the premier international congress in the field of applied mathematics held every four years under the auspices of the International Council for Industrial and Applied Mathematics.From August 10 to 14,2015,mathematicians,scientists     

Towards Excellence in Science Chinese Academy of Sciences

<正>May 26,2014,Beijing Science is a human enterprise in the pursuit of knowledge.The scientific revolution that occurred in the 17th Century initiated the advances of modern science.The scientific knowledge system created by     

Bounds for the zeros of polynomials

Let P(z)=∑↓j=0↑n ajx^j be a polynomial of degree n. In this paper we prove a more general result which interalia improves upon the bounds of a class of polynomials. We also prove a result which includes some extensions and generalizations of Enestrǒm-Kakeya theorem.     

Boundedness of commutators related to Marcinkiewicz integrals on hardy type spaces

In this paper, the authors study the boundedness of the operator [μΩ, b], the commutator generated by a function b ∈ Lipβ(Rn)(0 ＜β≤ 1) and the Marcinkiewicz integrals μΩ, on the classical Hardy spaces and the Herz-type Hardy spaces in the case Ω∈ Lipα(Sn-1)(0 ＜α≤ 1).     

Jacobi polynomials used to invert the laplace transform

Given the Laplace transform F(s) of a function f(t), we develop a new algorithm to find an approximation to f(t) by the use of the classical Jacobi polynomials. The main contribution of our work is the development of a new and very effective method to determine the coefficients in the finite series expansion that approximation f(t) in terms of Jacobi polynomials. Some numerical examples are illustrated.     

Generalization of the interaction between Haar approximation and polynomial operators to higher order methods

In applications it is useful to compute the local average empirical statistics on u. A very simple relation exists when of a function f（u） of an input u from the local averages are given by a Haar approximation. The question is to know if it holds for higher order approximation methods. To do so, it is necessary to use approximate product operators defined over linear approximation spaces. These products are characterized by a Strang and Fix like condition. An explicit construction of these product operators is exhibited for piecewise polynomial functions, using Hermite interpolation. The averaging relation which holds for the Haar approximation is then recovered when the product is defined by a two point Hermite interpolation.