FISCHER DECOMPOSITIONS OF ENTIRE FUNCTIONS OF HILBERT–SCHMIDT HOLOMORPHY TYPE

2004 ◽  
Vol 07 (02) ◽  
pp. 233-247
Author(s):  
HENRIK PETERSSON
Keyword(s):  
Hilbert Space ◽  
Entire Functions ◽  
Goursat Problem ◽  
Closed Operator ◽  
Multiplication Operators ◽  
Well Posedness ◽  
Homogeneous Polynomials ◽  
Fischer Decomposition ◽  
Linear Maps ◽  
Densely Defined

A Fischer pair (FP) for a vector space E is a pair (u, v) of linear maps on E, not necessarily everywhere defined, such that E= ker u⊕ Im v (Fischer decomposition). Thus, in particular, every densely defined closed operator u on a Hilbert space E forms a Fischer pair together with its adjoint u*, whenever Im u, or equivalently, Im u* is closed since then Im u*= ker u⊥. The question of when a given pair of maps (u, v) is a FP is related to the well-posedness of the (abstract) Cauchy–Goursat problem for u, v in E. We establish some Fischer pairs, for spaces that are built up by homogeneous Hilbert–Schmidt polynomials on a Hilbert space, consisting of differential and multiplication operators. In particular we study Fischer decompositions of the space of entire functions of Hilbert–Schmidt type. As a basis we generalize Fischers theorem for homogeneous polynomials in n variables to Hilbert–Schmidt polynomials.

A Uniqueness Theorem on the Degenerate Cauchy Problem(1)

1975 ◽  
Vol 18 (3) ◽  
pp. 417-421 ◽  
Author(s):  
Chung-Lie Wang
Keyword(s):  
Hilbert Space ◽  
Cauchy Problem ◽  
Uniqueness Theorem ◽  
Separable Hilbert Space ◽  
Adjoint Operator ◽  
Continuous Linear ◽  
Linear Maps ◽  
Image Position ◽  
Degenerate Cauchy Problem ◽  
Densely Defined

In [4] Carroll and the author have treated the following problem(1)where Λ is a closed densely defined self-adjoint operator in a separable Hilbert space H with (Λu, u) ≥ c ‖u‖2, c > 0, Λ-1 ∊ L(H) (L(E, F) is the space of continuous linear maps from E to F; in particular, L(H) = L(H, H)), a(t) > 0 for t > 0 a(0) = 0 and S(t), R(t), B(t) ∈ L(H).

scholarly journals Bitraces on PartialO*-Algebras

2007 ◽  
Vol 2007 ◽  
pp. 1-19
Author(s):  
G. O. S. Ekhaguere
Keyword(s):  
Hilbert Space ◽  
Linear Maps ◽  
Densely Defined

Unbounded bitraces on partialO*-algebras are considered, a class of ideals defined by them is exhibited, and several relationships between certain commutants, bicommutants, and tricommutants associated with the*-representations and*-antirepresentations determined by the bitraces are established. Moreover, a notion of a partialW*-algebra of unbounded densely defined linear maps on a Hilbert space, as a generalization of aW*-algebra, is introduced and a set of criteria for classifying such algebras by means of the type of bitraces that are defined on them is proposed.

scholarly journals Basic properties of unbounded weighted conditional type operators

Filomat ◽  
2021 ◽  
Vol 35 (2) ◽  
pp. 367-379
Author(s):  
Xiao-Feng Liu ◽  
Yousef Estaremi
Keyword(s):  
Hilbert Space ◽  
Spectral Radius ◽  
Polar Decomposition ◽  
Dense Subset ◽  
Multiplication Operators ◽  
Lp Space ◽  
Lp Spaces ◽  
Basic Properties ◽  
Densely Defined

In this paper we consider unbounded weighted conditional type (WCT) operators on Lp-space. We provide some conditions under which WCT operators on Lp-spaces are densely defined. Specifically, we obtain a dense subset of their domain. Moreover, we get that a WCT operator is continuous if and only if it is every where defined. A description of polar decomposition, spectrum, spectral radius, normality and hyponormality of WCT operators in this context are provided. Finally, we apply some results of hyperexpansive operators to WCT operators on the Hilbert space L2(?). As a consequence hyperexpansive multiplication operators are investigated.

scholarly journals Ordered Structures of Constructing Operators for Generalized Riesz Systems

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Hiroshi Inoue
Keyword(s):  
Hilbert Space ◽  
Ordered Set ◽  
Closed Operator ◽  
Inner Product ◽  
Maximal Elements ◽  
Ordered Structures ◽  
Minimal Elements ◽  
Riesz System ◽  
Densely Defined

A sequence {φn} in a Hilbert space H with inner product <·,·> is called a generalized Riesz system if there exist an ONB e={en} in H and a densely defined closed operator T in H with densely defined inverse such that {en}⊂D(T)∩D((T-1)⁎) and Ten=φn, n=0,1,⋯, and (e,T) is called a constructing pair for {φn} and T is called a constructing operator for {φn}. The main purpose of this paper is to investigate under what conditions the ordered set Cφ of all constructing operators for a generalized Riesz system {φn} has maximal elements, minimal elements, the largest element, and the smallest element in order to find constructing operators fitting to each of the physical applications.

Formally Normal Operators Having no Normal Extensions

1965 ◽  
Vol 17 ◽  
pp. 1030-1040 ◽  
Author(s):  
Earl A. Coddington
Keyword(s):  
Hilbert Space ◽  
Linear Operator ◽  
Null Space ◽  
Normal Operator ◽  
Closed Linear Operator ◽  
Normal Operators ◽  
The Given ◽  
Densely Defined ◽  
Made In

The domain and null space of an operator A in a Hilbert space will be denoted by and , respectively. A formally normal operatorN in is a densely defined closed (linear) operator such that , and for all A normal operator in is a formally normal operator N satisfying 35 . A study of the possibility of extending a formally normal operator N to a normal operator in the given , or in a larger Hilbert space, was made in (1).

scholarly journals Dirac structures on Hilbert spaces

1999 ◽  
Vol 22 (1) ◽  
pp. 97-108 ◽  
Author(s):  
A. Parsian ◽  
A. Shafei Deh Abad
Keyword(s):  
Hilbert Space ◽  
Linear Operator ◽  
Hilbert Spaces ◽  
Smooth Manifold ◽  
Real Hilbert Space ◽  
Dirac Structure ◽  
Dirac Structures ◽  
Basic Properties ◽  
Hilbert Subspace ◽  
Densely Defined

For a real Hilbert space(H,〈,〉), a subspaceL⊂H⊕His said to be a Dirac structure onHif it is maximally isotropic with respect to the pairing〈(x,y),(x′,y′)〉+=(1/2)(〈x,y′〉+〈x′,y〉). By investigating some basic properties of these structures, it is shown that Dirac structures onHare in one-to-one correspondence with isometries onH, and, any two Dirac structures are isometric. It is, also, proved that any Dirac structure on a smooth manifold in the sense of [1] yields a Dirac structure on some Hilbert space. The graph of any densely defined skew symmetric linear operator on a Hilbert space is, also, shown to be a Dirac structure. For a Dirac structureLonH, everyz∈His uniquely decomposed asz=p1(l)+p2(l)for somel∈L, wherep1andp2are projections. Whenp1(L)is closed, for any Hilbert subspaceW⊂H, an induced Dirac structure onWis introduced. The latter concept has also been generalized.

Three Test Problems for Quasisimilarity

1987 ◽  
Vol 39 (4) ◽  
pp. 880-892 ◽  
Author(s):  
Hari Bercovici
Keyword(s):  
Hilbert Space ◽  
Hilbert Spaces ◽  
Linear Operators ◽  
Structure Theory ◽  
Test Problems ◽  
Unitary Equivalence ◽  
Bounded Operators ◽  
Bounded Linear Operators ◽  
Bounded Linear ◽  
Densely Defined

Kaplansky proposed in [7] three problems with which to test the adequacy of a proposed structure theory of infinite abelian groups. These problems can be rephrased as test problems for a structure theory of operators on Hilbert space. Thus, R. Kadison and I. Singer answered in [6] these test problems for the unitary equivalence of operators. We propose here a study of these problems for quasisimilarity of operators on Hilbert space. We recall first that two (bounded, linear) operators T and T′ acting on the Hilbert spaces and , are said to be quasisimilar if there exist bounded operators and with densely defined inverses, satisfying the relations T′X = XT and TY = YT′. The fact that T and T′ are quasisimilar is indicated by T ∼ T′. The problems mentioned above can now be formulated as follows.

Regularly solvable extensions of non-self-adjoint ordinary differential operators

1984 ◽  
Vol 97 ◽  
pp. 79-95 ◽  
Author(s):  
W. D. Evans
Keyword(s):  
Hilbert Space ◽  
Weighted Space ◽  
Differential Operators ◽  
Linear Operators ◽  
Order Linear ◽  
Adjoint Pair ◽  
Closed Operators ◽  
Ordinary Differential Operators ◽  
Linear Differential ◽  
Densely Defined

SynopsisLetL0,M0be closed densely defined linear operators in a Hilbert spaceHwhich form an adjoint pair, i.e.. In this paper, we study closed operatorsSwhich satisfyand are regularly solvable in the sense of Višik. The abstract results obtained are applied to operators generated by second-order linear differential expressions in a weighted spaceL2(a, b; w).

scholarly journals A Similarity Invariant and the Commutant of some Multiplication Operators on the Sobolev Disk Algebra

2012 ◽  
Vol 2012 ◽  
pp. 1-17
Author(s):  
Ruifang Zhao
Keyword(s):  
Sobolev Space ◽  
Unit Disk ◽  
Analytic Functions ◽  
Entire Functions ◽  
Rational Functions ◽  
Multiplication Operators ◽  
Disk Algebra ◽  
Strongly Irreducible ◽  
Similarity Invariant ◽  
Sobolev Disk Algebra

LetR(𝔻)be the algebra generated in Sobolev spaceW22(𝔻)by the rational functions with poles outside the unit disk𝔻¯. In this paper, we study the similarity invariant of the multiplication operatorsMginℒ(R(𝔻)), whengis univalent analytic on𝔻orMgis strongly irreducible. And the commutants of multiplication operators whose symbols are composite functions, univalent analytic functions, or entire functions are studied.

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