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We consider Hilbert spaces of analytic functions in the disk with a normalized reproducing kernel and such that the backward shift $f(z) \mapsto \frac{f(z)-f(0)}{z}$ is a contraction on the space. We present a model for this operator and…

Functional Analysis · Mathematics 2019-01-15 Alexandru Aleman , Bartosz Malman

We consider three problems connected with coinvariant subspaces of the backward shift operator in Hardy spaces $H^p$: 1) properties of truncated Toeplitz operators; 2) Carleson-type embedding theorems for the coinvariant subspaces; 3)…

Functional Analysis · Mathematics 2022-02-28 Anton Baranov , Roman Bessonov , Vladimir Kapustin

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

A complete characterization of nearly-invariant subspaces of finite defect for the backward shift operator acting on the Hardy space is provided in the spirit of Hitt and Sarason's theorem. As a corollary we describe the almost-invariant…

Functional Analysis · Mathematics 2019-05-21 Isabelle Chalendar , Eva A. Gallardo-Gutiérrez , Jonathan R. Partington

It is well known that subspaces of the Hardy space over the unit disk which are invariant under the backward shift occur as the image of an observability operator associated with a discrete-time linear system with stable state-dynamics, as…

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

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 property of being shift invariant and being reflexive or transitive in the case of the space of (asymmetric) truncated Toeplitz operators, and the space of (asymmetric) dual truncated operators is investigated. Most of the results…

Functional Analysis · Mathematics 2022-03-18 M. Cristina Câmara , Kamila Kliś-Garlicka , Bartosz Łanucha , Marek Ptak

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

We consider an action of the circle group, T on a von Neumann algebra, M. Similarly to the case when the algebra of essentially bounded functions on T is acted upon by translations, we define the generalized Hardy subspace of H,where H is…

Operator Algebras · Mathematics 2019-04-30 Costel Peligrad

Compared with harmonic Bergman spaces, this paper introduces a new function space which is called the pluriharmonic Hardy space $h^{2}(\mathbb{T}^{2})$. We character (semi-) commuting Toeplitz operators on $h^{2}(\mathbb{T}^{2})$ with…

Functional Analysis · Mathematics 2016-12-08 Yuanqi Sang , Xuanhao Ding

In the authors' first paper, Beurling-Rudin-Korenbljum type characterization of the closed ideals in a certain algebra of holomorphic functions was used to describe the lattice of invariant subspaces of the shift plus a complex Volterra…

Complex Variables · Mathematics 2018-02-27 Bhupendra Paudyal , Zeljko Cuckovic

Operators of multiplication by independent variables on the space of square summable functions over the torus and its Hardy subspace are considered. Invariant subspaces where the operators are compatible are described.

Functional Analysis · Mathematics 2022-11-04 Zbigniew Burdak , Marek Kosiek , Patryk Pagacz , Marek Słociński

Let T be a C_{\cdot 0}-contraction on a Hilbert space H and S be a non-trivial closed subspace of H. We prove that S is a T-invariant subspace of H if and only if there exists a Hilbert space D and a partially isometric operator \Pi :…

Functional Analysis · Mathematics 2013-10-01 Jaydeb Sarkar

In this paper we present some consequences of the description of matrix representations of asymmetric truncated Toeplitz operators acting between finite-dimensional model spaces. In particular, we prove that these operators can be…

Functional Analysis · Mathematics 2020-07-29 Bartosz Łanucha

Truncated Toeplitz operators and their asymmetric versions are studied in the context of the Hardy space $H^p$ of the half-plane for $1<p<\infty$. It is shown that they are equivalent after extension to $2 \times 2$ matricial Toeplitz…

Functional Analysis · Mathematics 2015-04-27 M. Cristina Câmara , Jonathan R. Partington

This paper deals with representing in concrete fashion those Hilbert spaces that are vector subspaces of the Hardy spaces $H^p(\bb D^n) \ (1\le p\le \infty)$ that remain invariant under the action of coordinate wise multiplication by an…

Functional Analysis · Mathematics 2022-01-19 Sneh Lata , Sushant Pokhriyal , Dinesh Singh

We study the strong continuity of weighted composition semigroups of the form $T_tf=\varphi_t'\left(f\circ\varphi_t\right)$ in several spaces of analytic functions. First we give a general result on separable spaces and use it to prove that…

Functional Analysis · Mathematics 2017-06-29 Irina Arévalo , Marcos Oliva

We generalise the result of Berger and Shaw the trace formula for Hardy Hilbert space to a larger class of rotation invariant Hilbert function spaces on the unit disk. We also demonstrate many meaningful examples of these Hilbert spaces by…

Functional Analysis · Mathematics 2025-08-06 Nathan Parker

It is known that (i) a subspace ${\mathcal N}$ of the Hardy space $H^2$ which is invariant under the backward shift operator can be represented as the range of the observability operator of a conservative discrete-time linear system, (ii)…

Functional Analysis · Mathematics 2022-05-03 Joseph A. Ball , Vladimir Bolotnikov

This paper focuses on representations of contractively embedded invariant subspaces in several variables. We present a version of the de Branges theorem for $n$-tuples of multiplication operators by the coordinate functions on analytic…

Functional Analysis · Mathematics 2018-03-28 Sushil Gorai , Jaydeb Sarkar