Existence of singular extremals and singular functionals in reachable spaces

Given a linear, infinite dimensional control system with point target and "full" control we show that singular extremals for the minimum norm problem exist except in certain exceptional cases ("singular" means "not satisfying Pontryagin's maximum principle"). Existence of singular extremals implies existence of certain functionals (also called singular) in the space of reachable states. Received March 5, 2001; accepted April 10, 2001.     

Banach 空间中多值非单调算子的相补问题

应用H-空间中的Park极大元定理,在Banach空间中证明了多值非单调算子的相补问题的解的存在性定理．     

多值单调算子的隐补问题

在Banach空间中引入了多值算子的隐补问题和相补问题的新概念，并证明了多值单调算子隐补问题和相补问题解的存在性定理。     

Yet on linear structures of norm-attaining functionals on Asplund spaces

In this paper, we show that if an Asplund space X is either a Banach lattice or a quotient space of C(K), then it can be equivalently renormed so that the set of norm-attaining functionals contains an infinite dimensional closed subspace of X^* if and only if X^* contains an infinite dimensional reflexive subspace, which gives a partial answer to a question of Bandyopadhyay and Godefroy.     

一致光滑Banach空间内多值单调算子不动点的迭代

本文在一致光滑Ｂａｎａｃｂ空间中，讨论了满足一个单调型条件的多值映射的不动点的迭代过程。     

Reflexivity of Powers of the Multiplication Operator on Special Function Spaces

In this paper we present sufficient conditions for reflexivity of any powers of the multiplication operator acting on Banach spaces of formal Laurent series.     

自反Banach空间上算子代数的超自反性

本文引入自发Banach空间上算子代数A的超自反定义，讨论了A超自反的充要条件，超自反常数的估计以及超自反在代数同构下的不变性。     

Pseudo-differential operators on Sobolev and Lipschitz spaces

In this paper, by discovering a new fact that the Lebesgue boundedness of a class of pseudo- differential operators implies the Sobolev boundedness of another related class of pseudo-differential operators, the authors establish the boundedness of pseudo-differential operators with symbols in Sρ,δ^m on Sobolev spaces, where ∈ R, ρ≤ 1 and δ≤ 1. As its applications, the boundedness of commutators generated by pseudo-differential operators on Sobolev and Bessel potential spaces is deduced. Moreover, the boundedness of pseudo-differential operators on Lipschitz spaces is also obtained.     

On farthest points of sets

For a convex closed bounded set in a Banach space, we study the existence and uniqueness problem for a point of this set that is the farthest point from a given point in space. In terms of the existence and uniqueness of the farthest point, as well as the Lipschitzian dependence of this point on a point in space, we obtain necessary and su.cient conditions for the strong convexity of a set in several infinite-dimensional spaces, in particular, in a Hilbert space. A set representable as the intersection of closed balls of a fixed radius is called a strongly convex set. We show that the condition “for each point in space that is sufficiently far from a set, there exists a unique farthest point of the set” is a criterion for the strong convexity of a set in a finite-dimensional normed space, where the norm ball is a strongly convex set and a generating set.     

Fixed Point of Multivalued Operators on Partial Metric Spaces

In this paper, we prove some results on fixed point of multivalued operators on partial metric spaces.     

一类非线性算子的不动点定理及其应用

本文利用半序方法讨论了u0凹、-u0凸算子的不动点存在唯一性定理及迭代序列的收敛性问题,还讨论了序凹、序凸算子及u0凸算子的有关问题及它们在Ham- merstein型积分方程中的应用.所得结论推广并改进了已有的相关结论.     

关于Lipschitz映射空间的可余子空间

该文研究Lipschitz映射空间作为一个Banach空间的结构性质，主要研究了它的闭子空间有界线性算子空间（赋予算子范数）在其中的可余性．     

Lipschitz强增生算子方程逼近解的带误差的Ishikawa迭代程序

设E是任意实Banach空间，T：E→E是Ligpschitz的强增生算子。证明了带误差的Ishikawa迭代序列强收敛到方程Tx=f的唯一解。特别地，还给出了Ishikawa迭代序列的收敛率估计。另一方面，一个相关结果，讨论了E中Lipschitz强伪压缩映象的不动点的带误差的Ishikawa迭代序列的收敛性。     

Modified mann iterations for nonexpansive semigroups in Banach space

Let E be a real reflexive Banach space which admits a weakly sequentially continuous duality mapping from E to E^＊, and C be a nonempty closed convex subset of E. Let {T（t） ： t ≥ 0} be a nonexpansive semigroup on C such that F ：=∩t≥0 Fix（T（t）） ≠ 0, and f ： C → C be a fixed contractive mapping. If {αn}, {βn}, {an}, {bn}, {tn} satisfy certain appropriate conditions, then we suggest and analyze the two modified iterative processes as：{yn=αnxn＋（1-αn）T（tn）xn,xn=βnf（xn）＋（1-βn）yn
{u0∈C,vn=anun＋（1-an）T（tn）un,un＋1=bnf（un）＋（1-bn）vn
We prove that the approximate solutions obtained from these methods converge strongly to q ∈∩t≥0 Fix（T（t））, which is a unique solution in F to the following variational inequality：
〈（I-f）q,j（q-u）〉≤0 u∈F Our results extend and improve the corresponding ones of Suzuki [Proc. Amer. Math. Soc., 131, 2133-2136 （2002）], and Kim and XU [Nonlear Analysis, 61, 51-60 （2005）] and Chen and He [Appl. Math. Lett., 20, 751-757 （2007）].     

Exposed points and extremal problems in H1 on a bidisc

An essential bounded function ? gives a continuous linear functional on the Hardy space H¹ on the bitorus. In this paper, we consider extremal problems on H¹ when ? is a rational function, ? is a product of one variable functions or ? = |f|/f for some outer function f in H¹ such that f(z, w) has a good property with respect to w for a.e. z. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the H-property of functionals in Sobolev spaces

In this paper, we consider special classes of strongly convex functionals in Sobolev spaces. It is proved that functionals from such classes have the so-called H-property: weak convergence of sequences of arguments and convergence of such sequences with respect to a given functional imply strong convergence.Translated from Matematicheskie Zametki, vol. 77, no. 3, 2005, pp. 378–394.Original Russian Text Copyright © 2005 by A. S. Leonov.This revised version was published online in April 2005 with a corrected issue number.     

Random fixed points of asymptotically nonexpansive random operators on unbounded domains

The aim of this paper is to prove some random fixed point theorems for asymptotically nonexpansive random operator defined on an unbounded closed and starshaped subset of a Banach space.      

环同构及完全保持乘子不动点的映射

令${\mathcal R}_1$, ${\mathcal R}_2$为两个含单位元$I$的环. 在${\mathcal R}_1$某些温和的假设条件下, 本文基于对完全保持乘子不动点映射的分类研究, 给出${\mathcal R}_1$到${\mathcal R}_2$的环同态和环同构的刻画. 然后给出在Banach代数、套代数、矩阵代数以及标准算子代数等算子代数方面的应用.     

Lipschitz强增生算子方程解的Ishikawa迭代逼近

设E是任意实Banach空间．T：E→E是Lipschitz强增生算子,在无需假设limαn=limβn=0之下，本文证明了带误差的Ishikawa迭代序列强收敛到方程Tx=f的唯一解，而且还提供了该序列的某些特例的收敛率估计，另外，相关结果也讨论了E中Lipschkz强伪压缩映象的不动点的Ishikawa迭代逼近问题．本文结果改进并推广了文献中的一些最近结果。