共查询到20条相似文献,搜索用时 15 毫秒
1.
Israel Feldman Naum Krupnik Ilya Spitkovsky 《Integral Equations and Operator Theory》1996,24(1):68-80
The norm of the above-mentioned operatorS is computed on the unions of parallel lines or concentric circles. The upper bound is found for its norm on the ellipse. In case of weighted spaces on the unit circle, the exact norm is found for some rational weights, and necessary and sufficient conditions on the weight are established, under which the essential norm ofS equals 1. 相似文献
2.
A. Rogozhin 《Integral Equations and Operator Theory》2007,57(2):283-301
In this paper we estimate the norm of the Moore-Penrose inverse T(a)+ of a Fredholm Toeplitz operator T(a) with a matrix-valued symbol a∈LN × N∞ defined on the complex unit circle. In particular, we show that in the ”generic case” the strict inequality ||T(a)+|| > ||a−1||∞ holds. Moreover, we discuss the asymptotic behavior of ||T(tra)+|| for
. The results are illustrated by numerical experiments. 相似文献
3.
We prove analogues of the Brown-Halmos and Nehari theorems on
the norms of Toeplitz and Hankel operators, respectively, acting on subspaces
of Hardy type of reflexive rearrangement-invariant spaces with nontrivial Boyd
indices. 相似文献
4.
We solve a certain differential equation and system of integral equations. As applications, we characterize holomorphic symbols of commuting Toeplitz operators on the pluriharmonic Bergman space. In addition, pluriharmonic symbols of normal Toeplitz operators are characterized. Also, zero semi-commutators for certain classes of Toeplitz operators are characterized.This research is partially supported by KOSEF(98-0701-03-01-5). 相似文献
5.
6.
V. A. Khatskevich M. I. Ostrovskii V. S. Shulman 《Integral Equations and Operator Theory》2005,51(1):109-119
Inspired by some problems on fractional linear transformations the authors introduce and study the class of operators satisfying the condition
where stands for the spectral radius; and the class of Banach spaces in which all operators satisfy this condition, the authors call such spaces V-spaces. It is shown that many well-known reflexive spaces, in particular, such spaces as Lp(0,1) and Cp, are non-V-spaces if p 2; and that the spaces lp are V-spaces if and only if 1 < p < . The authors pose and discuss some related open problems. 相似文献
7.
Yuri I. Karlovich Enrique Ramírez de Arellano 《Integral Equations and Operator Theory》2001,39(4):441-474
LetB be the Banach algebra of all bounded linear operators on the weighted Lebesgue spaceL
p (T, ) with an arbitrary Muckenhoupt weight on the unit circleT, and
the Banach subalgebra ofB generated by the operators of multiplication by piecewise continuous coefficients and the operatorse
h,S
T
e
h,
–1
I (hR, T) whereS
T is the Cauchy singular integral operator ande
h,(t)=exp(h(t+)/(t–)),tT. The paper is devoted to a symbol calculus, Fredholm criteria and an index formula for the operators in the algebra
and its matrix analogue
. These shift-invariant algebras arise naturally in studying the algebras of singular integral operators with coefficients admitting semi-almost periodic discontinuities and shifts being diffeomorphisms ofT onto itself with second Taylor derivatives.Partially supported by CONACYT grant, Cátedra Patrimonial, No. 990017-EX and by CONACYT project 32726-E, México. 相似文献
8.
9.
Zen Harper 《Journal of Evolution Equations》2005,5(3):387-405
We study convolution operators on weighted Lebesgue spaces and obtain weight characterisations for boundedness of these operators
with certain kernels. Our main result is Theorem 3 which enables us to obtain results for certain kernel functions supported
on bounded intervals; in particular we get a direct proof of the known characterisations for Steklov operators in Section
3 by using the weighted Hardy inequality. Our methods also enable us to obtain new results for other kernel functions in Section
4. In Section 5 we demonstrate that these convolution operators are related to operators arising from the Weiss Conjecture
(for scalar-valued observation functionals) in linear systems theory, so that results on convolution operators provide elementary examples of nearly bounded semigroups
not satisfying the Weiss Conjecture. Also we apply results on the Weiss Conjecture for contraction semigroups to obtain boundedness
results for certain convolution operators. 相似文献
10.
11.
R. T. Rau 《Integral Equations and Operator Theory》1992,15(3):479-495
I wish to thank R. Nagel for his guidance and suggestions in the preparation of this paper. Also, I would like to thank G. Greiner and F. Räbiger for many interesting and helpful discussions. 相似文献
12.
We give results on the boundedness and compactness of localization
operators with two admissible wavelets on
for the Weyl-Heisenberg
group. 相似文献
13.
The problem we consider is how to obtain a UL-factorization from a LU-factorization for integral operators with semi-separable kernels in both the time varying and the time invariant cases. We also consider the special situation where the integral operators are self-adjoint. 相似文献
14.
Let Cp be the Schatten p-class for p>0. Generalizations of the parallelogram law for the Schatten 2-norms have been given in the following form: if A={A1,A2,…,An} and B={B1,B2,…,Bn} are two sets of operators in, then C2
15.
This paper studies various aspects of reproducing kernel spaces with a possibly indefinite metric when the field of scalar is replaced by the skew–field of quaternions. We first discuss in some details the positive case. A key fact which allows to consider the non–positive case is that Hermitian matrices with quaternionic entries have only real eigenvalues. This permits to extend the notion of functions with a finite number of negative squares to the present setting and we prove in particular that there is a one–to–one correspondence between such functions and reproducing kernel Pontryagin quaternionic spaces. 相似文献
16.
17.
The main objective is the study of a class of boundary value problems in weak formulation where two boundary conditions are
given on the half-lines bordering the first quadrant that contain impedance data and oblique derivatives. The associated operators
are reduced by matricial coupling relations to certain boundary pseudodifferential operators which can be analyzed in detail.
Results are: Fredholm criteria, explicit construction of generalized inverses in Bessel potential spaces, eventually after
normalization, and regularity results. Particular interest is devoted to the impedance problem and to the oblique derivative
problem, as well. 相似文献
18.
M. Faierman R. J. Fries R. Mennicken M. Möller 《Integral Equations and Operator Theory》2000,38(1):9-27
We determine the essential spectrum of the linearized Navier-Stokes operator with physical boundary conditions. In contrast to other approaches we do not make use of pseudo-differential operators. We establish a direct proof using only some fundamental results for matrix operators.Supported in part by a grant from the NRF of South Africa and by the John Knopfmacher Centre for Applicable Analysis and Number Theory, University of the Witwatersrand, Johannesburg 相似文献
19.
Rodolfo H. Torres 《Journal of Fourier Analysis and Applications》1998,4(3):283-297
The oscillatory behavior of functions with compactly supported Fourier transform is characterized in a quantified way using
various function spaces. In particular, the results in this article show that the oscillations of a function at large scale
are comparable to the oscillations of its samples on an appropriate discrete set of points. Several open questions about spaces
of sequences are answered and applications in the study of commutator operators on the Paley-Wiener space are shown.
Acknowledgements and Notes. Supported in part by NSF grants DMS 9303363 and DMS 9623251. 相似文献
20.
In this paper we obtain estimates, convergence results and rate of approximation for functions belonging to BV–spaces (spaces
of functions with bounded variation) by means of nonlinear convolution integral operators. We treat both the periodic and
the non-periodic case using, respectively, the classical Jordan variation and the multidimensional variation in the sense
of Tonelli. 相似文献