Smooth functions onC(K)

We show that every Fréchet differentiable real function onC(K), K scattered with locally uniformly continuous derivative has locally compact derivative. Using this and similar results, we investigate the existence ofC ²-Fréchet smooth surjections between various Banach spaces.     

Barrelledness conditions onC 0 (E)

Some conditions of barrelledness are considered and studied on the spaceC ₀(E), defined as follows: IfE is a real or complex Hausdorff locally convex space and \(P_E \) is a saturated family of seminorms, defining the original topology ofE, then the vector space of all the sequences \(\bar f = \left\{ {\bar f(n): n \in \mathbb{N}} \right\}\) inE, convergent to zero, provided with the locally convex topology $$\bar p(\bar f) = sup\left\{ {p (\bar f(n)): n \in \mathbb{N}} \right\}p \in P_E $$ is defined as the spaceC ₀(E). The main result of the paper is the following characterization:C ₀(E) is quasibarrelled (see [3], p. 367) if and only if,E is quasibarrelled and the strong dual ofE has property (B) (see [5], p. 30, for definition). We obtain. as a consequence, commutativity properties of the operatorC ₀, acting on certain inductive limits (3.3 Theorem). We also prove thatC ₀ does not commute with uncountably strict inductive limits. In particular, there are ultrabornological spacesE for whichC ₀(E) is not quasibarrelled. 3.1. Example provides a complete?-tensor product of two complete ultrabornological spaces which is not quasibarrelled.     

Uniformly ergodic maps onC*-algebras 027

LetT be an identity preserving Schwarz map on aC ^*-algebra. The following conditions are proved to be equivalent: (a)T is uniformly ergodic with finite-dimensional fixed space. (b)T is quasi-compact.     

3×3上三角算子矩阵的Weyl型定理

设A∈B(H1),B∈B(H2),C∈B(H3)为给定的三个算子,用M(D,E,F)= 表示一个作用在H1(?)H2(?)H3上的3×3算子矩阵．本文首先给出存在算子D∈B(H2,H1),E∈B(H3,H1),F∈B(H3,H2),使得M(D,E,F)为上半Fredholm算子(下半Fredholm算子)的充要条件．同时研究了3×3算子矩阵 M(D,E,F)的Weyl定理,α-Weyl定理,Browder定理和α-Browder定理．     

Linearization of holomorphic mappings onC(K)-spaces

We prove a universal mapping theorem for “integral” holomorphic mappings on the open unit ball ofC(K). In our theorem, the universal space isC(K), and the universal mapping is increasing in the positive cone ofC(K).     

Area of Julia sets of holomorphic self-maps onC *

It is a general problem to study the measure of Julia sets. There are a lot of results for rational and entire functions. In this note, we describe the measure of Julia set for some holomorphic self-maps onC ^*. We'll prove thatJ(f) has positive area, wheref:C ^*→C ^*,f(z)=z ^m c ^P(z)+Q(1/z) ,P(z) andQ(z) are monic polynomials of degreed, andm is an integer.     

Continuous selections for the metric projection onC 1

C ₁(K) is the space of real continuous functions onK endowed with the usualL ₁,-norm where \(K = \overline {\operatorname{int} K}\) is compact inR ^{m · U} is a finite-dimensional subspace ofC ₁,(K). The metric projection ofC ₁,(K) ontoU contains a continuous selection with respect toL ₁, -convergence if and only ifU is a unicity (Chebyshev) space forC ₁,(K). Furthermore, ifK is connected andU is not a unicity space forC ₁,(K), then there is no continuous selection with respect toL _∞-convergence. An example is given of aU and a disconnectedK with no continuous selection with respect toL ₁-convergence, but many continuous selections with respect toL _∞-convergence.     

Norm-attaining functionals onC(Q, X)

Functionals (vector measures) defined on the spaceC(Q, X) of continuous abstract functions (whereQ is a compact Hausdorff space andX is a Banach space) and attaining their norm on the unit sphere are considered. A characterization of such functionals is given in terms of the Radon-Nikodym derivative of the vector measure with respect to the variation of the measure and in terms of analogs of the derivative. Applications to the characterization of finite-codimensional subspaces with the best approximation property are given. Similar results are obtained for the spaceB(Q, Σ, X) of uniform limits of simple functions. Translated fromMatematicheskie Zametki, Vol. 61, No. 1, pp. 45–56, January, 1997. Translated by V. E. Nazaikinskii     

A note onC P estimates for certain kernels

For a certain class of operators defined by integral kernels, a necessary and sufficient condition is given for the belonging to the Schatten-von Neumann idealsC _P. The operators considered generalize the classical Hankel operators; the results thus extend Peller's characterization of the Hankel operators in a classC _P.