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1.
A detailed study is made of matrix-valued, ordinary linear differential operators T in for 1 < p < ∞, which arise as the perturbation of a constant coefficient differential operator of order n ≥ 1 by a lower order differential operator which has a factorisation S = AB for suitable operators A and B. Via techniques from L
p
-harmonic analysis, perturbation theory and local spectral theory, it is shown that T satisfies certain local resolvent estimates, which imply the existence of local functional calculi and decomposability properties
of T.
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2.
3.
S. Shkarin 《Integral Equations and Operator Theory》2009,64(1):115-136
It is shown that if 1 < p < ∞ and X is a subspace or a quotient of an ℓp-direct sum of finite dimensional Banach spaces, then for any compact operator T on X such that ∥I + T∥ > 1, the operator I + T attains its norm. A reflexive Banach space X and a bounded rank one operator T on X are constructed such that ∥I + T∥ > 1 and I + T does not attain its norm.
The author would like to thank E. Shargorodsky for his interest and comments. 相似文献
4.
Fritz Gesztesy Mark Malamud Marius Mitrea Serguei Naboko 《Integral Equations and Operator Theory》2009,64(1):83-113
We study generalized polar decompositions of densely defined closed linear operators in Hilbert spaces and provide some applications
to relatively (form) bounded and relatively (form) compact perturbations of self-adjoint, normal, and m-sectorial operators.
Based upon work partially supported by the US National Science Foundation under Grant Nos. DMS-0400639 and FRG-0456306, and
the Austrian Science Fund (FWF) under Grant No. Y330. 相似文献
5.
We revisit the boundedness of Hankel and Toeplitz operators acting on the Hardy space H
1 and give a new proof of the old result stating that the Hankel operator H
a
is bounded if and only if a has bounded logarithmic mean oscillation. We also establish a sufficient and necessary condition for H
a
to be compact on H
1. The Fredholm properties of Toeplitz operators on H
1 are studied for symbols in a Banach algebra similar to C + H
∞ under mild additional conditions caused by the differences in the boundedness of Toeplitz operators acting on H
1 and H
2.
The first author was partially supported by the European Commission IHP Network “Harmonic Analysis and Related Problems” (Contract
Number: HPRN-CT-2001-00273-HARP) and by the Greek Research Program “Pythagoras 2” (75% European funds and 25 National funds).
The second author was fully supported by the European Commission IHP Network “Harmonic Analysis and Related Problems” (Contract
Number: HPRN-CT-2001-00273-HARP) while he visited the first author at the University of Crete and later by the Academy of
Finland Project 207048. 相似文献
6.
Dr. Mohammed Hichem Mortad 《Integral Equations and Operator Theory》2009,64(3):399-408
We give a spectral analysis of some unbounded normal product HK of two self-adjoint operators H and K (which appeared in [7]) and we say why it is not self-adjoint even if the spectrum of one of the operators is sufficiently
“asymmetric”. Then, we investigate the self-adjointness of KH (given it is normal) for arbitrary self-adjoint H and K by giving a counterexample and some positive results and hence finishing off with the whole question of normal products of
self-adjoint operators (appearing in [1, 7, 12]).
The author was supported in part by CNEPRU: B01820070020 (Ministry of Higher Education, Algeria). 相似文献
7.
Victor D. Didenko 《Complex Analysis and Operator Theory》2008,2(2):345-359
Two types of estimate for the spectral radius of the multivariate refinement operator with power diagonal dilations are presented.
One type contains multiplicator norm of number matrices generated by the symbol of the corresponding operator and by specific
subsets of repeating fractions. These subsets are used together with the little Fermat theorem to establish estimates that
comprise integrals over tori of various dimensions. Moreover, we note certain classes of symbols when the exact value of the
spectral radius of refinement operator can be found. For the spectral radius of subdivision operators point value estimates
are established.
Submitted: April 25, 2007. Accepted: November 5, 2007. 相似文献
8.
Let A
0, ... , A
n−1 be operators on a separable complex Hilbert space , and let α0,..., α
n−1 be positive real numbers such that 1. We prove that for every unitarily invariant norm,
for 2 ≤ p < ∞, and the reverse inequality holds for 0 < p ≤ 2. Moreover, we prove that if ω0,..., ω
n−1 are the n roots of unity with ω
j
= e
2πij/n
, 0 ≤ j ≤ n − 1, then for every unitarily invariant norm,
for 2 ≤ p < ∞, and the reverse inequalities hold for 0 < p ≤ 2. These inequalities, which involve n-tuples of operators, lead to natural generalizations and refinements of some of the classical Clarkson inequalities in the
Schatten p-norms. Extensions of these inequalities to certain convex and concave functions, including the power functions, are olso
optained.
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9.
Elena Litsyn 《Integral Equations and Operator Theory》2007,58(2):239-253
The new definition of Volterra operator introduced in [5] allows specification of the classical theory of linear equations
in Banach spaces to equations with such operators. Here we specially address relations between properties of the given linear
equation with Volterra operator and properties of its conjugate. As well we treat the theory of Noetherian and Fredholm equations. 相似文献
10.
Tomas Ya. Azizov Jussi Behrndt Peter Jonas Carsten Trunk 《Integral Equations and Operator Theory》2009,63(2):151-163
For closed linear operators or relations A and B acting between Hilbert spaces and the concepts of compact and finite rank perturbations are defined with the help of the orthogonal projections P
A
and P
B
in onto the graphs of A and B. Various equivalent characterizations for such perturbations are proved and it is shown that these notions are a natural
generalization of the usual concepts of compact and finite rank perturbations.
Sadly, our colleague and friend Peter Jonas passed away on July, 18th 2007. 相似文献
11.
V. A. Khatskevich M. I. Ostrovskii V. S. Shulman 《Integral Equations and Operator Theory》2007,59(1):19-34
Properties of sets of solutions to inequalities of the form
are studied, where A, B, C are bounded Hilbert space operators, A and C are self-adjoint. Properties under consideration: closeness and interior points in standard operator topologies, convexity,
non-emptiness. 相似文献
12.
In this paper, we introduce Xia spectra of n-tuples of operators satisfying |T
2| ≥ U|T
2|U* for the polar decomposition of T = U|T| and we extend Putnam’s inequality to these tuples [7].
This research is partially supported by Grant-in-Aid Research No.17540176. 相似文献
13.
Andrzej Kryczka 《Integral Equations and Operator Theory》2008,61(4):559-572
We introduce the arithmetic separation of a sequence—a geometric characteristic for bounded sequences in a Banach space which
describes the Banach-Saks property. We define an operator seminorm vanishing for operators with the Banach-Saks property.
We prove quantitative stability of the seminorm for a class of operators acting between l
p
-sums of Banach spaces. We show logarithmically convex-type estimates of the seminorm for operators interpolated by the real
method of Lions and Peetre.
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14.
We introduce the notion of spectralizable operators. A closed operator A in a Hilbert space is called spectralizable if there exists a non-constant polynomial p such that the operator p(A) is a scalar spectral operator in the sense of Dunford. We show that such operators belongs to the class of generalized spectral
operators and give some examples where spectralizable operators occur naturally.
Vladimir Strauss gratefully acknowledges support by DFG, Grant No. TR 903/3-1. 相似文献
15.
Oscar F. Bandtlow 《Integral Equations and Operator Theory》2008,61(1):21-43
For a, α > 0 let E(a, α) be the set of all compact operators A on a separable Hilbert space such that s
n
(A) = O(exp(-anα)), where s
n
(A) denotes the n-th singular number of A. We provide upper bounds for the norm of the resolvent (zI − A)−1 of A in terms of a quantity describing the departure from normality of A and the distance of z to the spectrum of A. As a consequence we obtain upper bounds for the Hausdorff distance of the spectra of two operators in E(a, α).
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16.
M. A. Nudelman 《Integral Equations and Operator Theory》2007,58(2):273-299
Let
I
m
is the identity matrix of order m. Let W(λ) be an entire matrix valued function of order 2m, W(0) = I
2m
, the values of W(λ) are j
mm
-unitary at the imaginary axis and strictly j
mm
-expansive in the open right half-plane. The blocks of order m of the matrix W(λ) with appropriate signs are treated as coefficients of algebraic Riccati equation. It is proved that for any λ with positive
real part this equation has a unique contractive solution θ(λ). The matrix valued function θ(λ) can be represented in a form θ(λ) = θ
A
(iλ) where θ
A
(μ) is the characteristic function of some maximal dissipative operator A. This operator is in a natural way constructed starting from the Hamiltonian system of the form
with periodic coefficients. 相似文献
17.
Let be a multiplicative semigroup of positive operators on a Banach lattice E such that every is ideal-triangularizable, i.e., there is a maximal chain of closed subspaces of E that consists of closed ideals invariant under S. We consider the question under which conditions the whole semigroup is simultaneously ideal-triangularizable. In particular, we extend a recent result of G. MacDonald and H. Radjavi. We also
introduce a class of positive operators that contains all positive abstract integral operators when E is Dedekind complete.
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18.
Muneo Chō Mariko Giga Tadasi Huruya Takeaki Yamazaki 《Integral Equations and Operator Theory》2007,57(3):303-308
Let
be an invertible class A operator such that
. Then we show that
, where gT is the principal function of T. Moreover, we show that if T is pure, then
. 相似文献
19.
It is well known that there are classes of test functions such that a Hankel operator is bounded if and only if it is bounded
on those functions. Criteria are derived which determine whether a Hankel operator is compact or belongs to a particular Schatten
class, in terms of its action on those test functions. 相似文献
20.
Donald Sarason 《Integral Equations and Operator Theory》2008,61(2):281-298
This partly expository article develops the basic theory of unbounded Toeplitz operators on the Hardy space H
2, with emphasis on operators whose symbols are not square integrable. Unbounded truncated Toeplitz operators on coinvariant
subspaces of H
2 are also studied.
In memory of Paul R. Halmos 相似文献