共查询到20条相似文献,搜索用时 15 毫秒
1.
Dumitru Popa 《Quaestiones Mathematicae》2018,41(5):683-692
We prove two characterizations of new Cohen summing bilinear operators. The first one is: Let X, Y and Z be Banach spaces, 1 < p < ∞, V : X × Y → Z a bounded linear operator and n ≥ 2 a natural number. Then V is new Cohen p-summing if and only if for all Banach spaces X1,?…?, Xn and all p-summing operators U : X1 × · · · × Xn → X, the operator V ? (U, IY) : X1 × · · · × Xn × Y → Z is -summing. The second result is: Let H be a Hilbert space,, Y, Z Banach spaces and V : H × Y → Z a bounded bilinear operator and 1 < p < ∞. Then V is new Cohen p-summing if and only if for all Banach spaces E and all p-summing operators U : E → H, the operator V ? (U, IY) is (p, p*)-dominated. 相似文献
2.
David Pérez-García 《Archiv der Mathematik》2005,85(3):258-267
Let C denote the composition operator defined on the standard Hardy spaces Hp as
where is an analytic self-map of the unit disk in the complex plane. In this paper we discuss those invariant subspaces of C in Hp which are invariant under the shift operator,
We restrict our attention to the case where is an inner function. Our main result characterises these invariant subspaces. We also consider C when restricted to such an invariant subspace and we describe the structure of the operator and find a formula for the essential spectral radius.Received: 27 January 2004 相似文献
3.
Absolutely summing operators and local unconditional structures 总被引:5,自引:0,他引:5
4.
Daniel Alpay Piet Bruinsma Aad Dijksma Henk de Snoo 《Integral Equations and Operator Theory》1992,15(3):378-388
By an oversight on the part of the authors this section was not included in the paper previously published in Integral Equations Operator Theory, volume 14/4 (1991), 466–500.
Present address:Department of Mathematics Ben-Gurion University of the Negev Beersheva Israel 相似文献
5.
For a finite-dimensional linear subspace S⊆L(V,W) and a positive integer k, the k-reflexivity defect of S is defined by rdk(S)=dim(Refk(S)/S), where Refk(S) is the k-reflexive closure of S. We study this quantity for two-dimensional spaces of operators and for single generated algebras and their commutants. 相似文献
6.
Valentin Matache 《Integral Equations and Operator Theory》2001,39(3):329-334
A pull-back measure formula obtained in some particular cases by E. A. Nordgren and this author is generalized in the framework of boundary measures for zero-free Nevanlinna class fuctions on the unit polydisk. The formula is used to characterize the zero-free Nevanlinna class functions which are solutions of Schröder's equation induced by a polydisk automorphism (i.e. to determine the zero-free functionsf belonging to the Nevanlinna class which are solutions of the functional equationf ° =f, for some constant ), thus generalizing earlier results obtained by R. Mortini and this author. 相似文献
7.
The invertible, compact and Fredholm multiplication operators on Orlicz spaces are characterized in this paper. 相似文献
8.
We show contractibility to a point of the linear group for a wide class of symmetric spaces of measurable operators affiliated with several concrete non-atomic semifinite von Neumann algebras.Research supported by the Australian Research Council 相似文献
9.
M. Jasiczak 《Archiv der Mathematik》2006,87(5):436-448
We study regularity of Bergman and Szeg? projections on Sobolev type weighted-sup spaces. The paper covers the case of strongly
pseudoconvex domains with C4 boundary and, partially, domains of finite type in the sense of D’Angelo.
Received: 6 October 2005 相似文献
10.
In this paper we extend and generalize several known estimates for homogeneous polynomials and multilinear mappings on Banach spaces. Applying the theory of absolutely summing nonlinear mappings, we prove that estimates which are known for mappings on ?p spaces in fact hold true for mappings on arbitrary Banach spaces. 相似文献
11.
We introduce a general definition of almost
p-summing mappings and
give several concrete examples of such mappings. Some known results are
considerably generalized and we present various situations in which the
space of almost p-summing multilinear
mappings coincides with the whole space of continuous multilinear mappings.
Received: 17 June 2002 相似文献
12.
We consider hypercyclic composition operators on
which can be obtained from the translation operator using polynomial automorphisms of
. In particular we show that if C
S
is a hypercyclic operator for an affine automorphism S on
, then
for some polynomial automorphism Θ and vectors a and b, where I is the identity operator. Finally, we prove the hypercyclicity of “symmetric translations” on a space of symmetric analytic
functions on ℓ1.
Received: 8 June 2006 Revised: 26 September 2006 相似文献
13.
M.A. Sofi 《Indagationes Mathematicae》2009,20(2):273-284
We study the structure of Banach spaces X determined by the coincidence of nuclear maps on X with certain operator ideals involving absolutely summing maps and their relatives. With the emphasis mainly on Hilbert-space valued mappings, it is shown that the class of Hilbert—Schmidt spaces arises as a ‘solution set’ of the equation involving nuclear maps and the ideal of operators factoring through Hilbert—Schmidt maps. Among other results of this type, it is also shown that Hilbert spaces can be characterised by the equality of this latter ideal with the ideal of 2-summing maps. We shall also make use of this occasion to give an alternative proof of a famous theorem of Grothendieck using some well-known results from vector measure theory. 相似文献
14.
We present an abstract result that characterizes the coincidence of certain classes of linear operators with the class of Cohen strongly summing linear operators. Our argument is extended to multilinear operators and, as a consequence, we establish some alternative characterizations for the class of Cohen strongly summing multilinear operators. 相似文献
15.
We construct conjugate operators for the real part of a completely non-unitary isometry and we give applications to the spectral and scattering theory of a class of operators on (complete) Fock spaces, natural generalizations of the Schrödinger operators on trees. We consider C*-algebras generated by such Hamiltonians with certain types of anisotropy at infinity, we compute their quotient with respect to the ideal of compact operators, and give formulas for the essential spectrum of these Hamiltonians. 相似文献
16.
17.
B. Yousefi 《Archiv der Mathematik》2004,83(6):536-539
Let
be a Hilbert space of functions analytic on a plane domain such that for every in the functional of evaluation at is bounded. Assume further that
contains the constants and admits multiplication by the independent variable z, Mz, as a bounded operator. We give sufficient conditions for Mz to be reflexive.Received: 17 February 2004 相似文献
18.
Dietmar Vogt 《Archiv der Mathematik》2006,87(2):163-171
It is shown that for open convex
, d > 1 and a nontrivial polynomial P the space
does not have property
. If P is elliptic or homogeneous, then this holds for every open Ω. For
even
cannot occur and if it occurs for some Ω, then P must be hypoelliptic.
Received: 18 July 2005 相似文献
19.
Gerard J. Murphy 《Integral Equations and Operator Theory》1992,15(1):72-81
We consider the question of when a Toeplitz operator with continuous symbol on a connected compact abelian group is almost invertible, and show that this occurs precisely when the symbol is invertible and has zero topological index. The proof uses someK-theory computations. 相似文献
20.
Elias Flytzanis 《Monatshefte für Mathematik》1995,119(4):267-273
For a bounded linear operator in a complex separable Hilbert space we show that it accepts an invariant Borel probability measure of square integrable norm whose essential support spans the space, iff its eigenvectors with unimodular eigenvalues span the space.This research has been supported by the Economic Research Center (KOE) of the Athens University of Economics and Business. 相似文献