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Related papers: Concrete examples of $\mathscr{H}(b)$ spaces

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Using an explicit construction, we show that the de Branges-Rovnyak spaces $\mathscr{H}(b)$, corresponding to rational $b$, are contained in their associated Smirnov classes.

Complex Variables · Mathematics 2022-02-15 Emmanuel Fricain , Andreas Hartmann , William T. Ross , Dan Timotin

We describe de Branges-Rovnyak spaces $\mathcal H (b_{\alpha})$, $\alpha>0$, where the function $b_{\alpha}$ is not extreme in the unit ball of $H^{\infty}$ on the unit disk $\mathbb D$, defined by the equality…

Functional Analysis · Mathematics 2018-07-13 Bartosz Łanucha , Maria T. Nowak

Given a function $b$, holomorphic on the disc and bounded by 1, one can construct an associated reproducing kernel Hilbert space called the de Branges--Rovnyak space $H(b)$. We explore representations of such spaces via descriptions of the…

Complex Variables · Mathematics 2026-03-04 Eugenio Dellepiane , Daniel Seco

In this paper, we characterize the boundedness and the compactness of weighted composition operators acting on a de Branges-Rovnyak space $\mathcal H(b)$, where the symbol $b$ is a rational function in the unit ball of $H^\infty$ that is…

Complex Variables · Mathematics 2025-12-18 Emmanuel Fricain , Muath Karaki , Javad Mashreghi , Maëva Ostermann

For $b\in H^\infty_1$, the closed unit ball of $H^\infty$, the de Branges-Rovnyak spaces $\mathcal{H}(b)$ is a Hilbert space contractively contained in the Hardy space $H^2$ that is invariant by the backward shift operator $S^*$. We…

Functional Analysis · Mathematics 2018-10-03 Cheng Chu

In this paper, we study the cyclicity problem with respect to the forward shift operator $S_b$ acting on the de Branges--Rovnyak space $\mathscr{H}(b)$ associated to a function $b$ in the closed unit ball of $H^\infty$ and satisfying…

Functional Analysis · Mathematics 2022-10-31 Emmanuel Fricain , Sophie Grivaux

In most classical holomorphic function spaces on the unit disk, a function $f$ can be approximated in the norm of the space by its dilates $f\_r(z):=f(rz)~(r \textless{} 1)$. We show that this is \emph{not} the case for the de…

Functional Analysis · Mathematics 2015-01-14 O. El-Fallah , E. Fricain , K. Kellay , J. Mashreghi , Ransford Tom

Let $\mathcal{H}(b)$ be the de Branges-Rovnyak space associated to a non-extreme point $b$ of the unit ball of $H^\infty$, and let $\phi=b/a$, where $a$ is the Pythagorean mate of $b$. It is known that, if $f$ is a function holomorphic on a…

Complex Variables · Mathematics 2026-05-29 Thomas Ransford

In this paper, we study the de Branges-Rovnyak spaces $\mathcal{H}(B)$ generated by row Schur functions $B$ with mate $a$. We prove that the polynomials are dense in $\mathcal{H}(B)$, and characterize the backward shift invariant subspaces…

Functional Analysis · Mathematics 2024-10-01 Hongxin Chen , Caixing Gu , Shuaibing Luo

The de Branges--Rovnyak spaces are known to provide an alternate functional model for contractions on a Hilbert space, equivalent to the Sz.-Nagy--Foias model. The scalar de Branges--Rovnyak spaces $\mathcal{H}(b)$ have essentially…

Functional Analysis · Mathematics 2013-12-06 Javad Mashreghi , Dan Timotin

In most classical holomorphic function spaces on the unit disk in which the polynomials are dense, a function $f$ can be approximated in norm by its dilates $f_r(z):=f(rz)~(r<1)$, in other words, $\lim_{r\to1^-}\|f_r-f\|=0$. We construct a…

Complex Variables · Mathematics 2019-02-18 Javad Mashreghi , Thomas Ransford

In this paper, we characterize the boundedness, the compactness and the Hilbert-Schmidt property for composition operators acting from a de Branges-Rovnyak space $\mathcal H(b)$ into itself, when $b$ is a rational function in the closed…

Functional Analysis · Mathematics 2022-11-10 Rim Alhajj , Emmanuel Fricain

We show that there exists a de Branges-Rovnyak space $\mathcal{H}(b)$ on the unit disk containing a function $f$ with the following property: even though $f$ can be approximated by polynomials in $\mathcal{H}(b)$, neither the Taylor partial…

Functional Analysis · Mathematics 2021-09-07 Javad Mashreghi , Pierre-Olivier Parisé , Thomas Ransford

The de Branges-Rovnyak space $H(b)$ is generated by a bounded analytic function $b$ in the unit ball of $H^\infty$. When $b$ is a nonextreme point, the space $H(b)$ is invariant by the forward shift operator $M_z$. We show that the $H(b)$…

Functional Analysis · Mathematics 2023-09-25 Caixing Gu , Shuaibing Luo

We obtain orthogonal decompositions for de Branges-Rovnyak spaces $\H\left( \tfrac {I^n(1+I)}{2}\right)$ and $\H\left( \tfrac {I(1+I^2)}{2}\right)$, where $I$ is an inner function. We also discuss the problem of cyclicity for these spaces.

Functional Analysis · Mathematics 2025-06-16 Łanucha Bartosz , Michalska Małgorzata , Nowak Maria

The aim of this paper is to characterize universal and multiplier interpolating sequences for de Branges-Rovnyak spaces H (b) where the defining function b is a general non-extreme rational function. Our results carry over to recently…

Complex Variables · Mathematics 2025-12-11 Andreas Hartmann , Giuseppe Lamberti

We study conditions for containment of a given space $X$ of analytic functions on the unit disk $\mathbb{D}$ in the de Branges-Rovnyak space $\mathcal{H}(b)$. We deal with the non-extreme case in which $b$ admits a Pythagorean mate $a$, and…

Complex Variables · Mathematics 2024-04-02 Bartosz Malman , Daniel Seco

In this paper we discuss direct and reverse Carleson measures for the de Branges-Rovnyak spaces $\mathcal{H}(b)$, mainly when b is a non-extreme point of the unit ball of $H^{\infty}$.

Complex Variables · Mathematics 2013-08-08 Alain Blandignères , Emmanuel Fricain , Frederic Gaunard , Andreas Hartmann , Willam T. Ross

We discuss de Branges-Rovnyak spaces $\mathcal H(b)$ generated by nonextreme and rational functions $b$ and local Dirichlet spaces of order $m$ introduced in [6]. In [6] the authors characterized nonextreme $b$ for which the operator…

Functional Analysis · Mathematics 2023-06-13 Bartosz Łanucha , Małgorzata Michalska , Maria Nowak , Andrzej Sołtysiak

For the class of de Branges-Rovnyak spaces $\mathcal{H}(b)$ of the unit disk $\mathbb{D}$ defined by extreme points $b$ of the unit ball of $H^\infty$, we study the problem of approximation of a general function in $\mathcal{H}(b)$ by a…

Functional Analysis · Mathematics 2021-08-20 Adem Limani , Bartosz Malman
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