摘要:

The projection constants λ(Xn) of real n-dimensional symmetric spacesXnsatisfy asymptotically λ(Xn) ⪯ √n—4/√n which is smaller than for general spaces. For small dimensions, specific numerical values are obtained. For n = 2, we reprove the result of D.R. Lewis that λ(X2) ⪯ λ(l22) = 4/π for 2-dimensional symmetric spaces. If n > 2, however, λ(Xn) is generally larger than λ(ln2) for symmetric spaces. The method used is based on trace-duality and estimates involving symmetrically invariant spherical functions.

ISSN:1607-3606    

DOI:10.1080/16073606.1995.9631795

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This note contains an order-theoretical approach to the theory of stochastic operators. Our main result is a necessary condition for the existence of n-th roots of an ergodic and conservative operator, which generalizes known results for measure-preserving operators and operators onLp-type spaces.

ISSN:1607-3606    

DOI:10.1080/16073606.1995.9631796

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This is a report on a number of recent results on composition operators which map, for 0 <p⪯q∞, the Hardy spaceHp(on the unit disk in the complex plane) intoHq. Attention is focused on questions of boundedness (existence), compactness, order boundedness and, in connection with the latter, on relating the absolutely summing and nuclearity character as well as special factorization properties of the operator to function theoretic properties of the defining symbol. Moreover, tools are provided to show that certain classes of operators can well be distinguished already on the level of composition operators.

ISSN:1607-3606    

DOI:10.1080/16073606.1995.9631797

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Some well known properties of bounded weakly compact operators in Banach spaces are shown to be valid for arbitrary operators in normed spaces.

ISSN:1607-3606    

DOI:10.1080/16073606.1995.9631798

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We prove that if a unital Banach lattice algebra has sufficiently many one-dimensional elements and if its unit element has sufficiently many components then its positive elements have spectral properties analogous to those of positive operators on Banach lattices. In particular, if a positive element is irreducible (in the sense that (1—e)xe> 0 for all componentseof 1 satisfying 0 ≠e≠ 1) and compact, its spectral radius is positive and its spectrum shows cyclic behaviour.

ISSN:1607-3606    

DOI:10.1080/16073606.1995.9631799

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The powerful concept of an operator ideal on the class of all Banach spaces makes sense in the real and in the complex case. In both settings we may, for example, consider compact, nuclear, or 2-summing operators, where the definitions are adapted to each other in a natural way. This paper deals with the question whether or not that fact is based on a general philosophy. Does there exists a one-to-one correspondence between “real properties” and “complex properties” defining an operator ideal? In other words, does there exist for every real operator ideal a uniquely determined corresponding complex ideal and vice versa?

ISSN:1607-3606    

DOI:10.1080/16073606.1995.9631800

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A new proof of Durier's Theorem [3] concerning a characterization of Hilbert spaces in terms of the Fermat-Weber location problem will be presented.

ISSN:1607-3606    

DOI:10.1080/16073606.1995.9631801

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We define a new classBof sets of strongly summable and bounded sequences, determine their first and second α- and β-duals, and characterize linear operators on the spaces inB.

ISSN:1607-3606    

DOI:10.1080/16073606.1995.9631802

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:1607-3606    

DOI:10.1080/16073606.1995.9631803

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:1607-3606    

DOI:10.1080/16073606.1995.9631804

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor