误差估计中矩阵求逆条件数的最优性在Hilbert空间中的推广

本文利用Hilbert空间中可逆算子的极发解定理，将误差估计中矩阵求逆条件数的最优性在Hilbert空间中进行推广，证明了线性有界算子A的求逆条件数K(A)=‖A‖A^-1‖在求算子扰动逆(A E)^-1的相对误差界中的极小性质，指出了算子求逆条件数在误差估计为仅与算子A有关的最佳常数值。     

解不适定算子方程的一个定常二步隐式迭代法

１．引言 设Ｘ,Ｙ是两个Ｈｉｌｂｅｒｔ空间,Ａ：Ｘ→Ｙ是有界线性算子,考虑算子方程 Ａｘ＝ｙ（１．１）如果Ａ的值域Ｒ（Ａ）在Ｙ中非闭,则方程（１．１）是不适定的［１］．许多应用科学中都归结出这一类方程,特别地,许多反问题是不适定的［２,３］．本文考虑方程（１．１）的 Ｍｏｏｒｅ－Ｐｅｎｒｏｓｅ广义解,这里Ａ是算子Ａ的Ｍｏｏｒｅ－Ｐｅｎｒｏｓｅ广义逆［１］．Ａ＋ｙ存在当且仅当本文均作这一假设．在实际中,通常代替（１．１）的是扰动方程这里右端项,为一给定的误差水平,Ｑ是Ｙ到Ｒ（Ａ）的正交投影算子．对扰…     

映射F_p:X→‖AXB-C‖_p~p的临界点的特征

对于Ｈｉｌｂｅｒｔ空间上有界线性算子Ａ、Ｂ、Ｃ,考虑了当Ａ有一个广义逆Ａ~－使得（ＡＡ~－）~＊＝ＡＡ~－,Ｂ有一个广义逆 Ｂ~－使得（Ｂ~－ Ｂ）～＊＝ Ｂ~－ Ｂ时,映射 Ｆ_ｐ： Ｘ→｜｜ＡＸＢ－ Ｃ｜｜_ｐ~ｐ临界点的特征的一般形式（１＜ ｐ＜∞）,推广了Ｐ．Ｊ．Ｍａｈａｒ的关于对ｐ＝ ２时的结果,并指出该定理可推广到多个算子的情形．     

Hilbert空间上交换本质正规算子组的C_p－类扰动

本文证明了若Ｂ＝（Ｂ１，…，Ｂｎ）是Ｈｉｌｂｅｒｔ空间Ｈ上交换正规算子组，Ａ＝（Ａ１，…，Ａｎ）是Ｈ上交换本质正规算子组，Ｓｐ（Ｂ）Ｓｐｅ（Ａ），且Ｓｐ（Ｂ）的Ｈａｕｓｄｏｒｆｆ维数等于α，则对任意ε＞０及ｐ≥ｍａｘ（α＋ε，１），Ａ模Ｃｐ－近似酉等价于ＡＢ＝（Ａ１Ｂ１，……ＡｎＢｎ）．     

映射Fp：X→‖AXB—C‖p^p的临界点的特征

对于Ｈｉｌｂｅｒｔ空间有界线性算子Ａ、Ｂ、Ｃ,考虑了当Ａ有一个广义逆Ａ＾－使得（ＡＡ＾－）＾＊＝ＡＡ＾－,Ｂ有一个广义逆Ｂ＾－Ｔ使得（Ｂ＾－Ｂ）＾＊＝Ｂ＾－Ｂ时,映射Ｆｐ：Ｘ→‖ＡＸＢ－Ｃ‖ｐ＾ｐ临界点的特征的一般形式（１〈ｐ〈∞）,推广了Ｐ．Ｊ．Ｍａｈｅｒ的关于ｐ＝２时的结果,并指出该定理可推广到多个算子的情形。     

再生核空间扣的一类最佳逼近及其应用

在［１－２］中分别定义了具有再生核的Ｈｉｌｂｅｒｔ空间Ｗ＾１２［ａ，ｂ］和Ｗ，并给出再生核的解析式。本文讨论再生核空间中线性算子的一类最佳逼近，给出逼近算子的表达式及误差估计，作为特例得到类似于［１－４］中的插值的公公式，数值积分公式和数值原函数公式，但本文的公式计算更简便。     

Hilbert空间上交换自伴算子组的C_p－类扰动

本文证明，如果Ｈｉｌｂｅｒｔ空间上交换自伴算子组Ｔ＝（Ｔ１，…，Ｔｎ）的Ｔａｙｌｏｒ谱之Ｈａｕｓｄｏｒｆｆ直维数等于α，α≥１，则对任意的ｐ＞α，存在Ｃｐ－范数充分小的Ｃｐ－类算子组Ｋ，使得Ｔ－Ｋ是交换对角算子组。     

Banach空间中Moore-Penrose广义逆与不适定边值问题

设Ｘ，Ｙ为Ｂａｎａｃｈ空间，Ｄ（Ａ）Ｘ，Ａ：Ｄ（Ａ）→Ｙ为具有闭值域的闭稠定线性算子．本文不假设Ａ具有“定义域可分解”条件［１８］，引入Ａ的Ｍｏｏｒｅ－Ｐｅｎｒｏｓｅ广义逆Ａ＋．与Ｍ．Ｚ．Ｎａｓｈｅｄ引入的不同，Ａ＋一般非线性．本文在空间Ｘ，Ｙ的一定几何框架下，证得Ａ＋的存在唯一性、极小性、连续性，并给出了线性的充要条件，便于将Ａ＋应用于方程、优化、控制等问题．作为应用，本文第二部分利用Ｍｏｏｒｅ－Ｐｅｎｒｏｓｅ广义逆讨论空间ＬＰ（Ω）（１＜Ｐ）中一类不适定的边值问题．在另文，给出广义逆在控制论中的应用．     

周期mild解和算子半群的谱(英)

设Ｘ是Ｈｉｌｂｅｒｔ空间,ｅ~Ａｔ是Ｘ上的（１,Ａ）类半群．本文给出了用（λ－Ａ）~－１的性质来描述ｅ~Ａｔ谱的特征,同时也得到了Ｂａｎａｃｈ空间Ｘ中使（１,Ａ）类半群谱映射定理成立的一些充分条件．     

关于强拓扑对偶多重Hilbert空间上连续线性算子的（C_0，1）－发展系

本文证明：若强对偶多重Ｈｉｌｂｅｒｔ空间上的（Ｃ＿０，１）－半群族的无穷小生成算子族是г－稳定的，则该半群族生成г－稳定的发展系．基于此，本文还得出了关于（Ｃ＿０，１）－发展系的一个摄动定理．     

On the Minimum Property of the Pseudo $x$-Condition Number for a Linear Operator

It is well known that the $x$-condition number of a linear operator is a measure of ill condition with respect to its generalized inverses and a relative error bound with respect to the generalized inverses of operator $T$ with a small perturbation operator E, namely,$$\frac{\|(T+E)^+-T^+\|}{\|T^+\|}\leq \frac{x(T)\frac{\|E\|}{\|T\|}}{1-x(T)\frac{\|E\|}{\|T\|}},$$ where $x{T}=\|T\|\dot\|T^+\|$. The problem is whether there exists a positive number $μ(T)$ independent of $E$ but dependent on $T$ such that the above relative error bound holds and $μ(T)＜x(T)$.In this paper, an answer is given to this problem.     

Convexity with respect to a differential equation

The concepts of convexity of a set, convexity of a function and monotonicity of an operator with respect to a second-order ordinary differential equation are introduced in this paper. Several well-known properties of usual convexity are derived in this context, in particular, a characterization of convexity of function and monotonicity of an operator. A sufficient optimality condition for a optimization problem is obtained as an application. A number of examples of convex sets, convex functions and monotone operators with respect to a differential equation are presented.     

THE MINIMAL PROPERTY OF THE CONDITION NUMBER OF INVERTIBLE LINEAR BOUNDED OPERATORS IN BANACH SPACES

In this paper we show that in error estimates, the condition number k(T) of any in-vertible linear bounded operator T in Banach spaces is minimal. We also extend the Hahn-Ba-nach theorem and other related results.     

一类广义Lyapunov矩阵方程的正定解

研究了双线性系统中的一类广义Lyapunov矩阵方程的正定解.基于混合单调算子不动点定理,给出新的存在正定解的充分条件,构造了求其正定解的不动点迭代方法,并给出了迭代误差估计公式.数值实验表明新方法是可行的.     

Ball Convergence Theorems for Chebyshev-Halley Method in $\mathbb{B}$-Space

A local convergence analysis of Chebyshev-Halley method having third order of convergence for approximating zero of non-linear operator $f(v)=0$ by using convex majorant function and their condition in $\mathbb{B}$-space (Banach space), is presented in this article. We give the error estimate to show the efficiency of our study. Besides, we established the relation between majorant function and Kantorovich or Smale-type result as special cases of our general theory.     

Stability and Sensitivity of Tridiagonal LU Factorization without Pivoting

In this paper the accuracy of LU factorization of tridiagonal matrices without pivoting is considered. Two types of componentwise condition numbers for the L and U factors of tridiadonal matrices are presented and compared. One type is a condition number with respect to small relative perturbations of each entry of the matrix. The other type is a condition number with respect to small componentwise perturbations of the kind appearing in the backward error analysis of the usual algorithm for the LU factorization. We show that both condition numbers are of similar magnitude. This means that the algorithm is componentwise forward stable, i.e., the forward errors are of similar magnitude to those produced by a componentwise backward stable method. Moreover the presented condition numbers can be computed in O(n) flops, which allows to estimate with low cost the forward errors. AMS subject classification (2000) 65F35, 65F50, 15A12, 15A23, 65G50.Received October 2003. Accepted August 2004. Communicated by Per Christian Hansen.Froilán M. Dopico: This research has been partially supported by the Ministerio de Ciencia y Tecnología of Spain through grants BFM2003-06335-C03-02 (M. I. Bueno) and BFM2000-0008 (F. M. Dopico).     

C^n中子空间之间极端主角的一些应用

本文给出了Ｃ＾ｎ中子空间之间最大和最小主角在矩阵逼近，投影算子的扰动分析，群逆以及Ｏｒａｘｉｎ逆的扰动估计，条件数理论，Ｂｏｔｔ－Ｄｕｆｆｉｎ系统扰动分析中一些应用。     

Improved stability and error analysis for a class of local projection stabilizations applied to the Oseen problem

We consider a class of local projection stabilizations with projection spaces defined on (possibly) overlapping sets applied to the Oseen problem. We prove that the underlying bilinear form satisfies an inf–sup condition with respect to a stronger norm than coercivity suggests. A modification of the stabilization of the convection allows an optimal estimation of the consistency error. A priori estimates in the stronger norm and in the L² norm for the pressure are established. Discontinuous pressure approximations are included in the analysis. © 2012 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2013     

An Estimation of the Truncation Error for the Two-Channel Sampling Formulas

The aim of the article is to obtain an estimation for the truncation error in the two-channel sampling formulas. Since these formulas are expansions with respect to suitable Riesz bases in Paley-Wiener spaces, the truncation error will be estimated by using the hypercircle inequality in the Riesz bases setting. In so doing, the norm of an involved operator is calculated, and the remainder of the series of the absolute square sampling functions is estimated.     

A characteristic condition for convergence of steepest descent approximation to accretive operator equations

In the present paper a sufficient and necessary condition for convergence of steepest descent approximation to accretive operator equations is established, and for the sufficiency part a specific error estimation is also given.