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By a famous result, functions in backward shift invariant subspaces in Hardy spaces are characterized by the fact that they admit a pseudocontinuation a.e. on $\T$. More can be said if the spectrum of the associated inner function has holes…

Complex Variables · Mathematics 2008-10-22 Andreas Hartmann

This paper considers paired operators in the context of the Lebesgue Hilbert space on the unit circle and its subspace, the Hardy space $H^2$. The kernels of such operators, together with their analytic projections, which are…

Functional Analysis · Mathematics 2024-02-09 M. Cristina Câmara , Jonathan R. Partington

We present two novel results about Hilbert space operators which are nilpotent of order two. First, we prove that such operators are indestructible complex symmetric operators, in the sense that tensoring them with any operator yields a…

Functional Analysis · Mathematics 2012-07-17 Stephan Ramon Garcia , Bob Lutz , Dan Timotin

Given a contraction A on a Hilbert space H, an operator T on H is said to be A-invariant if <Tx,x>=<TAx,Ax> for every x in H such that ||Ax||=||x||. In the special case in which both defect indices of A are equal to 1, we show that every…

Functional Analysis · Mathematics 2017-05-01 H. Bercovici , D. Timotin

This paper offers a unified approach to determining when two generalized Toeplitz operators on L^2 are equivalent. This will be done through multipliers between closed subspaces of L^2. Our discussion will include Toeplitz operators (and…

Functional Analysis · Mathematics 2023-07-12 Cristina Camara , Carlos Carteiro. William T. Ross

This paper is a survey on the emerging theory of truncated Toeplitz operators. We begin with a brief introduction to the subject and then highlight the many recent developments in the field since Sarason's seminal paper in 2007.

Complex Variables · Mathematics 2012-06-25 Stephan Ramon Garcia , William T. Ross

This tutorial paper presents a survey of results, both classical and new, linking inner functions and operator theory. Topics discussed include invariant subspaces, universal operators, Hankel and Toeplitz operators, model spaces, truncated…

Functional Analysis · Mathematics 2015-03-19 Isabelle Chalendar , Pamela Gorkin , Jonathan R. Partington

We discuss resent developments in the problem of description of finite rank Toeplitz operators in different Bergman spaces and give some applications in analysis and mathematical physics

Functional Analysis · Mathematics 2009-04-02 Grigori Rozenblum

We consider the class of positive bounded and semi-continuous functions defined on the two dimensional torus If f belongs to this class, then f will be considered as the symbol of a Toeplitz operator truncated on a triangle parametrised by…

Functional Analysis · Mathematics 2013-02-26 Jean-Marc Rinkel , Abdellatif Seghier

We present complete characterizations of Toeplitz operators that are complex symmetric. This follows as a by-product of characterizations of conjugations on Hilbert spaces. Notably, we prove that every conjugation admits a canonical…

Functional Analysis · Mathematics 2022-07-27 Sudip Ranjan Bhuia , Deepak Pradhan , Jaydeb Sarkar

The paper gives the background for Toeplitz $T_a$ and Hankel $H_a$ operators acting between distinct Hardy type spaces over the unit circle $\mathbb{T}$. We characterize possible symbols of such operators and prove general versions of…

Functional Analysis · Mathematics 2018-02-09 Karol Lesnik

We define positive Toeplitz operators between weighted harmonic Bloch spaces $b^\infty_\alpha$ on the unit ball of $\mathbb{R}^n$ for the full range of parameter $\alpha\in\mathbb{R}$. We give characterizations of bounded and compact…

Complex Variables · Mathematics 2023-05-22 Ömer Faruk Doğan

We relate dual-band general Toeplitz operators to block truncated Toeplitz operators and, via equivalence after extension, with Toeplitz operators with $4 \times 4$ matrix symbols. We discuss their norm, their kernel, Fredhomlness,…

Functional Analysis · Mathematics 2021-06-04 M. Cristina Câmara , Ryan O'Loughlin , Jonathan R. Partington

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

We introduce a generalized Crofoot transform between the model spaces corresponding to matrix-valued inner functions. As an application, we obtain results about matrix-valued truncated Toeplitz operators.

Functional Analysis · Mathematics 2020-02-07 Rewayat Khan

In this paper we obtain a complete characterization of reducing, invariant, and hyperinvariant subspaces for the completely non-unitary component of a power partial isometry. In particular, precise characterization of reducing, invariant,…

Functional Analysis · Mathematics 2025-05-06 Kritika Babbar , Amit Maji

In this paper, we completely characterize when two dual truncated Toeplitz operators are essentially commuting and when the semicommutator of two dual truncated Toeplitz operators is compact. Our main idea is to study dual truncated…

Functional Analysis · Mathematics 2020-12-29 Chongchao Wang , Xianfeng Zhao , Dechao Zheng

It is well known that the kernel of a Toeplitz operator is nearly invariant under the backward shift $S^*$. This paper shows that kernels of finite-rank perturbations of Toeplitz operators are nearly $S^*$-invariant with finite defect. This…

Functional Analysis · Mathematics 2020-04-29 Yuxia Liang , Jonathan R. Partington

This paper addresses the question of how categorical symmetries act on extended operators in quantum field theory. Building on recent results in two dimensions, we introduce higher tube categories and algebras associated to higher fusion…

High Energy Physics - Theory · Physics 2023-05-30 Thomas Bartsch , Mathew Bullimore , Andrea Grigoletto

We study Toeplitz operator theory on the doubling Fock spaces, which are Fock spaces whose exponential weight is associated to a subharmonic function with doubling Riesz measure. Namely, we characterize the boundedness, compactness and…

Complex Variables · Mathematics 2015-08-13 Roc Oliver , Daniel Pascuas