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We give a few observations on different types of bounded operators on a topological vector space X and their relations with compact operators on X. In particular, we investigate when these bounded operators coincide with compact operators.…

Functional Analysis · Mathematics 2015-08-25 Ljubisa D. R. Kocinac , Omid Zabeti

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…

Functional Analysis · Mathematics 2008-11-11 Fritz Gesztesy , Mark Malamud , Marius Mitrea , Serguei Naboko

We study the compactness of composition operators on the Bergman spaces of certain bounded pseudoconvex domains in $\mathbb{C}^n$ with non-trivial analytic disks contained in the boundary. As a consequence we characterize that compactness…

Complex Variables · Mathematics 2020-06-12 Timothy G. Clos

The introduction of the categorical notion of closure operators has unified various important notions and has led to interesting examples and applications in diverse areas of mathematics (see for example, Dikranjan and Tholen (\cite{DT})).…

Category Theory · Mathematics 2010-10-22 Joaquin Luna-Torres , Carlos Orlando Ochoa C

We continue the study of multidimensional operator multipliers initiated in [arXiv:math/0701645]. We introduce the notion of the symbol of an operator multiplier. We characterise completely compact operator multipliers in terms of their…

Operator Algebras · Mathematics 2015-02-06 K. Juschenko , R. H. Levene , I. G. Todorov , L. Turowska

An improvement of the author's result, proved in 1961, concerning necessary and sufficient conditions for the compactness of embedding operators is given. A counterexample to a published statement concerning compactness of embedding…

Numerical Analysis · Mathematics 2007-05-23 A. G. Ramm

We consider composition operators in the Dirichlet space of the unit disc in the plane. Various criteria on boundedness, compactness and Hilbert-Schmidt class membership are established. Some of these criteria are shown to be optimal.

Functional Analysis · Mathematics 2010-12-30 O. El-Fallah , K. Kellay , M. Shabankhah , H. Youssfi

We discuss some results concerning fixed point equations in the setting of topological *-algebras of unbounded operators. In particular, an existence result is obtained for what we have called {\em weak $\tau$ strict contractions}, and some…

Mathematical Physics · Physics 2007-05-23 F. Bagarello

We characterize bounded and compact positive Toeplitz operators defined on the Bergman spaces over the Siegel upper half-space.

Complex Variables · Mathematics 2019-04-02 Congwen Liu , Jiajia Si

We use topological consequences of PFA, MA$_{\omega_1}$(S)[S] and PFA(S)[S] proved by other authors to show that normal first countable linearly H-closed spaces with various additionals properties are compact in these models.

General Topology · Mathematics 2023-08-25 Mathieu Baillif

For the set C(X) of real-valued continuous functions on a Tychonoff space X, the compact-open topology on C(X) is a "set-open topology". This paper studies the separation and countability properties of the space C(X) having the topology…

General Topology · Mathematics 2016-04-07 Anubha Jindal , R. A. McCoy , S. Kundu

When G is a region in the complex plane, compact composition operators on the uniform algebra of bounded analytic functions on G and the spectra of these operators were described by D. Swanton, Compact composition operators on B(D), Proc.…

Functional Analysis · Mathematics 2007-05-23 J. F. Feinstein , Herbert Kamowitz

Frame multipliers are an abstract version of Toeplitz operators in frame theory and consist of a composition of a multiplication operator with the analysis and synthesis operators. Whereas the boundedness properties of frame multipliers on…

Functional Analysis · Mathematics 2025-06-24 Peter Balazs , Karlheinz Gröchenig

We generalize some results on compact operators on Hilbert spaces to "compact" operators on some Hilbert right W*-modules. We present in this frame the Schatten decomposition of the compact operators, the trace, the Banach Lp-spaces and…

Operator Algebras · Mathematics 2014-03-27 Corneliu Constantinescu

We characterize those regular, holomorphic or formal maps into the orbit space $V/G$ of a complex representation of a finite group $G$ which admit a regular, holomorphic or formal lift to the representation space $V$. In particular, the…

Algebraic Geometry · Mathematics 2008-05-05 Andreas Kriegl , Mark Losik , Peter W. Michor , Armin Rainer

In this paper, the objects of our investigation are some dyadic operators, including dyadic shifts, multilinear paraproducts and multilinear Haar multipliers. We mainly focus on the continuity and compactness of these operators. First, we…

Classical Analysis and ODEs · Mathematics 2017-03-24 Heng Gu , Qingying Xue , Kozo Yabuta

We study the closure $\bar{CSO}$ of the set $CSO$ of all complex symmetric operators on a separable, infinite-dimensional, complex Hilbert space. Among other things, we prove that every compact operator in $\bar{CSO}$ is complex symmetric.…

Functional Analysis · Mathematics 2012-11-21 Stephan Ramon Garcia , Daniel E. Poore

This paper presents a few additions to commutant lifting theory. An operator interpolation problem is introduced and shown to be equivalent to the relaxed commutant lifting problem. Using this connection a description of all solutions of…

Functional Analysis · Mathematics 2007-05-23 A. E. Frazho , S. ter Horst , M. A. Kaashoek

In this paper, existence of pairs of solutions is obtained for compact potential operators on Hilbert spaces. An application to a second-order boundary value problem is also given as an illustration of our results.

Analysis of PDEs · Mathematics 2024-07-25 A. Mokhtari , K. Saoudi , D. D. Repovš

This paper characterises the boundedness and compactness of Agler--McCarthy monomial operators by reducing them to weighted composition operators and deriving explicit Carleson measure criteria on the half-plane. The results are illustrated…

Functional Analysis · Mathematics 2022-12-06 I. Chalendar , J. R. Partington