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Recently, it was shown that the image of a Toeplitz kernel of dimension greater than $1$ under composition by an inner function is nearly $S^*$-invariant if and only if the inner function is an automorphism. Building on this, we determine…

Functional Analysis · Mathematics 2025-10-08 Yuxia Liang , Jonathan R. Partington

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 aim of this paper is to investigate asymmetric truncated Toeplitz operators with $L^2$ symbols between two different model spaces given by inner functions such that one divides the other. Characterizations of these operators are given…

Functional Analysis · Mathematics 2017-10-18 Cristina Câmara , Joanna Jurasik , Kamila Kliś--Garlicka , Marek Ptak

In this paper, we give a characterization of all closed linear operators in a separable Hilbert space which are unitarily equivalent to an integral operator in $L_2(R)$ with bounded and arbitrarily smooth Carleman kernel on $R^2$. In…

Spectral Theory · Mathematics 2007-05-23 Igor M. Novitskii

This article describes Hilbert spaces contractively contained in certain reproducing kernel Hilbert spaces of analytic functions on the open unit disc which are nearly invariant under division by an inner function. We extend Hitt's theorem…

Functional Analysis · Mathematics 2025-02-19 Arshad Khan , Sneh Lata , Dinesh Singh

In this paper, we characterize all closed linear operators in a separable Hilbert space which are unitarily equivalent to an integral bi-Carleman operator in $L_2(R)$ with bounded and arbitrarily smooth kernel on $R^2$. In addition, we give…

Spectral Theory · Mathematics 2007-05-23 Igor M. Novitskii

This paper can be considered as the sequel of [6], where the authors have proposed an abstract construction of Hardy spaces H^1. They shew an interpolation result for these Hardy spaces with the Lebesgue spaces. Here we describe a more…

Classical Analysis and ODEs · Mathematics 2008-09-25 Frédéric Bernicot

We represent closed subspaces of the Hardy space that are invariant under finite-rank perturbations of the backward shift. We apply this to classify almost invariant subspaces of the backward shift and represent a more refined version of…

Functional Analysis · Mathematics 2024-08-09 Soma Das , Jaydeb Sarkar

We review some classical and more recent results concerning kernels of Toeplitz operators and their relations with model spaces, which are themselves Toeplitz kernels of a special kind. We highlight the fundamental role played by the…

Functional Analysis · Mathematics 2017-11-28 M. Cristina Câmara , Jonathan R. Partington

Truncated Toeplitz operators are compressions of Toeplitz operators on model spaces; they have received much attention in the last years. This survey article presents several recent results, which relate boundedness, compactness, and…

Functional Analysis · Mathematics 2016-01-08 Isabelle Chalendar , Emmanuel Fricain , Dan Timotin

In this note, we describe the backward shift invariant subspaces for a large class of reproducing kernel Hilbert spaces. This class includes in particular de Branges-Rovnyak spaces (the non-extreme case) and the range space of co-analytic…

Functional Analysis · Mathematics 2019-04-08 Emmanuel Fricain , Javad Mashreghi , Rishika Rupam

In this paper, we describe families of those bounded linear operators on a separable Hilbert space that are simultaneously unitarily equivalent to integral operators on $L_2(R)$ with bounded and arbitrarily smooth Carleman kernels. The main…

Spectral Theory · Mathematics 2007-05-23 Igor M. Novitskii

To help understand various reproducing kernels used in applied sciences, we investigate the inclusion relation of two reproducing kernel Hilbert spaces. Characterizations in terms of feature maps of the corresponding reproducing kernels are…

Functional Analysis · Mathematics 2011-06-22 Haizhang Zhang , Liang Zhao

We introduce a new class of conjugations and characterize complex symmetric Toeplitz operators on the Hardy space with respect to those conjugations. Also, we prove that complex symmetricity and \uet~ property are the same for a certain…

Functional Analysis · Mathematics 2021-07-15 Yong Chen , Young Joo Lee , Yile Zhao

The theory of Toeplitz quantization presented in our previous paper is extended and further developed to include diverse and interesting non-commutative realizations of the classical Euclidean plane. This is done using Hilbert spaces of…

Quantum Physics · Physics 2021-05-19 Micho Durdevich , Stephen Bruce Sontz

In this paper we study mapping properties of Toeplitz-like operators on weighted Bergman spaces of bounded strongly pseudconvex domains in $\mathbb{C}^n$. In particular we prove that a Toeplitz operator built using as kernel a weighted…

Complex Variables · Mathematics 2019-05-31 Marco Abate , Samuele Mongodi , Jasmin Raissy

We study the boundedness of composition operators on the bidisk using reproducing kernels. We show that a composition operator is bounded on the Hardy space of the bidisk if some associated function is a positive kernel. This positivity…

Complex Variables · Mathematics 2018-07-02 Cheng Chu

Let $H$ be a Schr\"odinger operator on $\R^n$. Under a polynomial decay condition for the kernel of its spectral operator, we show that the Besov spaces and Triebel-Lizorkin spaces associated with $H$ are well defined. We further give a…

Analysis of PDEs · Mathematics 2007-05-23 Shijun Zheng

We explore boundedness properties of kernel integral operators acting on rearrangement-invariant (r.i.) spaces. In particular, for a given r.i. space $X$ we characterize its optimal range partner, that is, the smallest r.i. space $Y$ such…

Functional Analysis · Mathematics 2022-11-11 Jakub Takáč

In this paper we consider asymmetric truncated Toeplitz operators acting between two finite-dimensional model spaces. We compute the dimension of the space of all such operators. We also describe the matrix representations of asymmetric…

Functional Analysis · Mathematics 2018-07-09 Joanna Jurasik , Bartosz Łanucha