共查询到20条相似文献,搜索用时 15 毫秒
1.
Yongjiang Duan 《Integral Equations and Operator Theory》2007,58(3):301-314
This paper is to study the quasihomogeneous Hilbert modules and generalize a result of Arveson [3] which relates the curvature
invariant to the index of the Dirac operator.
This work was partially supported by NKBRPC (#2006CB805905) and SRFDP. 相似文献
2.
Rongwei Yang 《Integral Equations and Operator Theory》2006,56(3):431-449
On the Hardy space over the bidisk H2(D2), the Toeplitz operators
and
are unilateral shifts of infinite multiplicity. A closed subspace M is called a submodule if it is invariant for both
and
. The two variable Jordan block (S1, S2) is the compression of the pair
to the quotient H2(D2) ⊖M. This paper defines and studies its defect operators. A number of examples are given, and the Hilbert-Schmidtness is proved
with good generality. Applications include an extension of a Douglas-Foias uniqueness theorem to general domains, and a study
of the essential Taylor spectrum of the pair (S1, S2). The paper also estabishes a clean numerical estimate for the commutator [S1*, S2] by some spectral data of S1 or S2. The newly-discovered core operator plays a key role in this study. 相似文献
3.
Peter Quiggin 《Integral Equations and Operator Theory》1993,16(2):244-266
Pick's theorem tells us that there exists a function inH
, which is bounded by 1 and takes given values at given points, if and only if a certain matrix is positive.H
is the space of multipliers ofH
2, and this theorem has a natural generalisation whenH
is replaced by the space of multipliers of a general reproducing kernel Hilbert spaceH(K) (whereK is the reproducing kernel). J. Agler has shown that this generalised theorem is true whenH(K) is a certain Sobolev space or the Dirichlet space, so it is natural to ask for which reproducing kernel Hilbert spaces this generalised theorem is true. This paper widens Agler's approach to cover reproducing kernel Hilbert spaces in general, replacing Agler's use of the deep theory of co-analytic models by a relatively elementary, and more general, matrix argument. The resulting theorem gives sufficient (and usable) conditions on the kernelK, for the generalised Pick's theorem to be true forH(K), and these are then used to prove Pick's theorem for certain weighted Hardy and Sobolev spaces and for a functional Hilbert space introduced by Saitoh. 相似文献
4.
We consider Hilbert spaces
of analytic functions defined on an open subset
of
, stable under the operator Mu of multiplication by some function u. Given a subspace
of
which is nearly invariant under division by u, we provide a factorization linking each element of
to elements of
on the inverse image under u of a certain complex disc, for which we give a relatively simple formula. By applying these results to
and u(z) = z, we obtain interesting results involving a H2-norm control. In particular, we deduce a factorization for the kernel of Toeplitz operators on Dirichlet spaces. Finally, we give a localization for the problem of extraneous zeros.Submitted: January 18, 2003 Revised: December 20, 2003 相似文献
5.
Schur multipliers on the unit ball are operator-valued functions for
which the N-variable Schwarz-Pick kernel is nonnegative. In this paper, the
coefficient spaces are assumed to be Pontryagin spaces having the same negative
index. The associated reproducing kernel Hilbert spaces are characterized
in terms of generalized difference-quotient transformations. The connection
between invariant subspaces and factorization is established. 相似文献
6.
Antonio G. García Miguel A. Hernández-Medina 《Mediterranean Journal of Mathematics》2005,2(3):345-356
Let
be a symmetric operator with compact resolvent defined in a Hilbert space
For any fixed
we consider an entire
function Ka which involves the resolvent of
Associated with Ka we obtain, by duality in
a Hilbert space
of entire functions which becomes a De Branges space of entire functions. This property provides a characterization of
regardless of the anti-linear mapping which has
as its range space. There exists also a sampling formula allowing to recover any function in
from its samples at the sequence of eigenvalues of
This work has been supported by the grant BFM2003–01034 from the D.G.I. of the Spanish Ministerio de Ciencia y Tecnología. 相似文献
7.
Operator ranges and non-cyclic vectors for the backward shift 总被引:2,自引:0,他引:2
Michael Sand 《Integral Equations and Operator Theory》1995,22(2):212-231
In this paper we look at operators on the Hardy spaceH
2(D) with range containing all of the non-cyclic vectors of the backward shift. We show several classes of such operators must be surjective, including Toeplitz, Hankel and composition operators. 相似文献
8.
W. Norrie Everitt Antonio G. García Miguel Angel Hernández-Medina 《Results in Mathematics》2008,51(3-4):215-228
The classical Kramer sampling theorem provides a method for obtaining orthogonal sampling formulas. A challenging problem
is to characterize the situations when these sampling formulas can be written as Lagrange-type interpolation series. This
article gives a necessary and sufficient condition to ensure that when the sampling formula is associated with an analytic
Kramer kernel, then it can be expressed as a quasi Lagrange-type interpolation series; this latter form is a minor but significant
modification of a Lagrange-type interpolation series. Finally, a link with the theory of de Branges spaces is established.
Received: October 8, 2007. Revised: December 13, 2007. 相似文献
9.
Characteristic Functions for Ergodic Tuples 总被引:1,自引:0,他引:1
Motivated by a result on weak Markov dilations, we define a notion of characteristic function for ergodic and coisometric
row contractions with a one-dimensional invariant subspace for the adjoints. This extends a definition given by G. Popescu.
We prove that our characteristic function is a complete unitary invariant for such tuples and show how it can be computed. 相似文献
10.
Dušan R. Georgijević 《Integral Equations and Operator Theory》2005,53(2):247-267
A mixed type, L?wner and Nevanlinna-Pick directional two-sided interpolation problem is considered. A necessary and sufficient
condition for the problem to have a solution is established, in terms of properties of the Pick kernel to the problem. As
well, a parametrization of the set of all real rational solutions of minimal degree is given. The corresponding Nevanlinna-Pick
boundary-interior interpolation problem is also considered and a solvability condition for it is obtained. The approach to
the problem is via functional Hilbert spaces. 相似文献
11.
The product of operators with closed range in Hilbert C-modules 总被引:1,自引:0,他引:1
K. Sharifi 《Linear algebra and its applications》2011,435(5):1122-1130
Suppose T and S are bounded adjointable operators with close range between Hilbert C∗-modules, then TS has closed range if and only if Ker(T)+Ran(S) is an orthogonal summand, if and only if Ker(S∗)+Ran(T∗) is an orthogonal summand. Moreover, if the Dixmier (or minimal) angle between Ran(S) and Ker(T)∩[Ker(T)∩Ran(S)]⊥ is positive and is an orthogonal summand then TS has closed range. 相似文献
12.
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
13.
We consider a generalization of isometric Hilbert space operators to the multivariable setting. We study some of the basic
properties of these tuples of commuting operators and we explore several examples. In particular, we show that the d-shift, which is important in the dilation theory of d-contractions (or row contractions), is a d-isometry. As an application of our techniques we prove a theorem about cyclic vectors in certain spaces of analytic functions
that are properly contained in the Hardy space of the unit ball of
. 相似文献
14.
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
15.
We prove L p Poincaré inequalities with suitable dimension free constants for functions on the discrete cube {?1, 1} n . As well known, such inequalities for p an even integer allow to recover an exponential inequality hence the concentration phenomenon first obtained by Bobkov and Götze. We also get inequalities between the L p norms of $ \left\vert \nabla f\right\vert We prove L
p
Poincaré inequalities with suitable dimension free constants for functions on the discrete cube {−1, 1}
n
. As well known, such inequalities for p an even integer allow to recover an exponential inequality hence the concentration phenomenon first obtained by Bobkov and
G?tze. We also get inequalities between the L
p
norms of and moreover L
p
spaces may be replaced by more general ones. Similar results hold true, replacing functions on the cube by matrices in the
*-algebra spanned by n fermions and the L
p
norm by the Schatten norm C
p
. 相似文献
16.
Saida Sultanic 《Integral Equations and Operator Theory》2006,55(4):573-595
The central question of this paper is the one of finding the right analogue of the Commutant Lifting Theorem for the Bergman
space La2. We also analyze the analogous problem for weighted Bergman spaces La,α2, − 1 < α < ∞. 相似文献
17.
18.
It is known that for particular classes of operators on certain reproducing
kernel Hilbert spaces, key properties of the operators (such as boundedness
or compactness) may be determined by the behaviour of the operators
on the reproducing kernels. We prove such results for Toeplitz operators on
the Paley-Wiener space, a reproducing kernel Hilbert space over
. Namely,
we show that the norm of such an operator is equivalent to the supremum of
the norms of the images of the normalised reproducing kernels of the space.
In particular, therefore, the operator is bounded exactly when this supremum
is finite. In addition, a counterexample is provided which shows that the operator
norm is not equivalent to the supremum of the norms of the images
of the real normalised reproducing kernels. We also give a necessary and
sufficient condition for compactness of the operators, in terms of their limiting
behaviour on the reproducing kernels. 相似文献
19.
Vern I. Paulsen 《Integral Equations and Operator Theory》2001,41(1):38-62
We prove that it is possible for two uniform algebras to have the same scalar interpolating sets, yet still have different matrix-valued interpolating sets.We prove a result for tensor products of uniform algebras that extends Agler's interpolation formula for the bidisk to more general product domains. This is accomplished by introducing a dual object for interpolation problems, which we call a Schur ideal, and proving that the Schur ideal for a tensor product is the intersection of the corresponding Schur ideals.Research supported in part by a grant from the NSF 相似文献
20.
This note presents a commutant lifting theorem (CLT) with initial data a finite set of (test) functions and a compatible reproducing
kernel k on a set X. This covers the CLT of Ball, Li, Timotin, and Trent [9] for the polydisc, but in general no analyticity is required, rather
statements and proofs use the language and techniques of reproducing kernel Hilbert spaces. Uniqueness of the de Branges–Rovnyak
construction like found in Agler [1] and Ambrozie, Englis, and Müller [5] and an abstract Beurling Theorem in the present
context are of independent interest.
Received: October 12, 2006. Accepted: May 8, 2007. 相似文献