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In this paper we consider compressions of $k^{th}$--order slant Toeplitz operators to the backward shift invariant subspaces of the classical Hardy space $H^2$. In particular, we characterize these operators using compressed shifts and…

Functional Analysis · Mathematics 2019-11-12 Bartosz Łanucha , Małgorzata Michalska

We study two extension problems, and their interconnections: (i) extension of positive definite (p.d.) continuous functions defined on subsets in locally compact groups $G$; and (ii) (in case of Lie groups $G$) representations of the…

Functional Analysis · Mathematics 2014-01-22 Palle Jorgensen , Steen Pedersen , Feng Tian

Two problems are posed that involve the star-invariant subspace $K^p_\theta$ (in the Hardy space $H^p$) associated with an inner function $\theta$. One of these asks for a characterization of the extreme points of the unit ball in…

Functional Analysis · Mathematics 2014-02-03 Konstantin M. Dyakonov

In this paper, the analysis of nearly invariant subspaces and kernels of Toeplitz operators on the Hardy space over the bidisk is developed. Firstly, we transcribe Chalendar, Chevrot and Partington's result to vector-valued Hardy space…

Functional Analysis · Mathematics 2025-09-18 Senhua Zhu , Yuxia Liang

We discuss relations between uniform minimality, unconditionality and interpolation for families of reproducing kernels in backward shift invariant subspaces. This class of spaces contains as prominent examples the Paley-Wiener spaces for…

Complex Variables · Mathematics 2009-01-23 Eric Amar , Andreas Hartmann

By applying methods of Duhamel algebra and reproducing kernels, we prove that every linear bounded operator on the Hardy-Hilbert space H^{2}(D) has a nontrivial invariant subspace. This solves affirmatively the Invariant Subspace Problem in…

Functional Analysis · Mathematics 2013-11-04 Mübariz Garayev

Recently, Liang and Partington \cite{YP} show that kernels of finite-rank perturbations of Toeplitz operators are nearly invariant with finite defect under the backward shift operator acting on the scalar-valued Hardy space. In this article…

Functional Analysis · Mathematics 2020-05-06 Arup Chattopadhyay , Soma Das , Chandan Pradhan

We consider the bosonic Fock space over the Hilbert space of transversal vector fields in three dimensions. This space carries a canonical representation of the group of rotations. For a certain class of operators in Fock space we show that…

Mathematical Physics · Physics 2015-05-28 David Hasler , Ira Herbst

In this paper we initiate the study of a fundamental yet untapped random model of non-selfadjoint, bounded linear operators acting on a separable complex Hilbert space. We replace the weights $w_n=1$ in the classical unilateral shift $T$,…

Functional Analysis · Mathematics 2018-11-15 Guozheng Cheng , Xiang Fang , Sen Zhu

The behavior of certain weighted Hardy-type operators on rearrangement-invariant function spaces is thoroughly studied with emphasis being put on the optimality of the obtained results. First, the optimal rearrangement-invariant function…

Functional Analysis · Mathematics 2023-08-14 Zdeněk Mihula

In this paper first we give a partial answer to a question of L. Moln\'ar and W. Timmermann. Namely, we will describe those linear (not necessarily bijective) transformations on the set of self-adjoint matrices which preserve a unitarily…

Functional Analysis · Mathematics 2015-07-13 György Pál Gehér , Gergő Nagy

A refined notion of curvature for a linear system of Hermitian vector spaces, in the sense of Grothendieck, leads to the unitary classification of a large class of analytic Hilbert modules. Specifically, we study Hilbert sub-modules, for…

Spectral Theory · Mathematics 2009-09-11 Shibananda Biswas , Gadadhar Misra , Mihai Putinar

It is known that the structure of invariant subspaces of the Hardy space $H^2(\mathbb D^n)$ on the polydisc $\mathbb{D}^n$ is very complicated; hence, we need good examples help us to understand the structure of invariant subspaces of…

Functional Analysis · Mathematics 2018-04-12 Beyaz Basak Koca

An interesting and recently much studied generalization of the classical Schur class is the class of contractive operator-valued multipliers $S$ for the reproducing kernel Hilbert space ${\mathcal H}(k_{d})$ on the unit ball ${\mathbb…

Classical Analysis and ODEs · Mathematics 2007-05-23 Joseph A. Ball , Vladimir Bolotnikov , Quanlei Fang

We study analytic models of operators of class $C_{\cdot 0}$ with natural positivity assumptions. In particular, we prove that for an $m$-hypercontraction $T \in C_{\cdot 0}$ on a Hilbert space $\mathcal{H}$, there exists a Hilbert space…

Functional Analysis · Mathematics 2016-02-26 Monojit Bhattacharjee , Jaydeb Sarkar

Recently a $f$-deformed Fock space which is spanned by $|n>_{\lambda}$ has been introduced. These bases are indeed the eigen-states of a deformed non-Hermitian Hamiltonian. In this contribution, we will use a rather new non-orthogonal basis…

Quantum Physics · Physics 2012-04-13 M K Tavassoly , M H Lake

In this paper we formulate the almost invariant subspaces theorems of backward shift operators in terms of the ranges or kernels of product of Toeplitz and Hankel operators. This approach simplifies and gives more explicit forms of these…

Functional Analysis · Mathematics 2024-11-21 Caixing Gu , In Sung Hwang , Hyoung Joon Kim , Woo Young Lee , Jaehui Park

The theory of dynamical frames evolved from practical problems in dynamical sampling where the initial state of a vector needs to be recovered from the space-time samples of evolutions of the vector. This leads to the investigation of…

Functional Analysis · Mathematics 2025-05-27 Victor Bailey , Deguang Han , Keri Kornelson , David Larson , Rui Liu

We consider an action of a compact group whose dual is archimedean linearly ordered or a direct product (or sum) of such groups on a von Neumann algebra, M. We define the generalized Hardy subspace of the Hilbert space of a standard…

Operator Algebras · Mathematics 2020-10-13 Costel Peligrad

In this paper we deal with a scale of reproducing kernel Hilbert spaces $H^{(n)}_2$, $n\ge 0$, which are linear subspaces of the classical Hilbertian Hardy space on the right-hand half-plane $\mathbb{C}^+$. They are obtained as ranges of…

Functional Analysis · Mathematics 2024-01-30 José E. Galé , Valentin Matache , Pedro J. Miana , Luis Sánchez--Lajusticia
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