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We give a sufficient condition for two operators to be disjointly frequently hypercyclic. We apply this criterion to composition operators acting on $H(\mathbb D)$ or on the Hardy space $H^2(\mathbb D)$. We simplify a result on disjoint…

Functional Analysis · Mathematics 2022-11-24 Frédéric Bayart

By a theorem of Gordon and Hedenmalm, $\varphi$ generates a bounded composition operator on the Hilbert space $\mathscr{H}^2$ of Dirichlet series $\sum_n b_n n^{-s}$ with square-summable coefficients $b_n$ if and only if $\varphi(s)=c_0…

Functional Analysis · Mathematics 2015-02-23 Hervé Queffélec , Kristian Seip

We show that there exist non-compact composition operators in the connected component of the compact ones on the classical Hardy space $H^2$ on the unit disc. This answers a question posed by Shapiro and Sundberg in 1990. We also establish…

Functional Analysis · Mathematics 2007-06-20 Eva A. Gallardo-Gutiérrez , Maria J. González , Pekka Nieminen , Eero Saksman

In this paper, we study the basic properties such as boundedness and compactness of composition operators on discrete analogue of generalized Hardy space defined on a homogeneous rooted tree. Also, we compute the operator norm of…

Functional Analysis · Mathematics 2016-10-03 Perumal Muthukumar , Saminathan Ponnusamy

In this paper, we investigate weighted composition, Volterra and Integral operators on second derivative Hardy spaces. Some equivalent conditions for boundedness of the operators will be given using the boundedness on the Hardy spaces. Also…

Functional Analysis · Mathematics 2022-10-13 Mostafa Hassanlou , Ebrahim Abbasi

This paper provides a class of complex symmetric weighted composition operators on $H^2(\mathbb{D})$ to includes the unitary subclass, the Hermitian subclass and the normal subclass obtained by Bourdon and Noor. A characterization of…

Functional Analysis · Mathematics 2018-12-27 Cao Jiang , Shi-An Han , Ze-Hua Zhou

By using the Schur test, we give some upper and lower estimates on the norm of a composition operator on $\mathcal{H}^2$, the space of Dirichlet series with square summable coefficients, for the inducing symbol $\varphi(s)=c_1+c_{q}q^{-s}$…

Functional Analysis · Mathematics 2018-02-07 Perumal Muthukumar , Saminathan Ponnusamy , Hervé Queffélec

We prove that a composition operator is bounded on the Hardy space $H^2$ of the right half-plane if and only if the inducing map fixes the point at infinity non-tangentially, and has a finite angular derivative $\lambda$ there. In this case…

Functional Analysis · Mathematics 2014-02-26 Sam Elliott , Michael T. Jury

Building on techniques used in the case of the disc, we use a variety of methods to develop formulae for the adjoints of composition operators on Hardy spaces of the upper half-plane. In doing so, we prove a slight extension of a known…

Functional Analysis · Mathematics 2008-10-14 Sam Elliott

In this paper, we provide some sufficient conditions for the compactness of weighted composition operators on Dirichlet space. Furthermore, we characterize the numerical range of certain classes of weighted composition operators on…

Functional Analysis · Mathematics 2026-01-05 Subhadip Halder , Sweta Mukherjee , Riddhick Birbonshi

We introduce and systematically study a class of operators that arise naturally due to the Beurling decomposition of the Hardy space $H^2=K_\theta \oplus \theta H^2$. While the compressions of classical Toeplitz and Hankel operators to the…

Functional Analysis · Mathematics 2026-04-02 Priyanka Aroda , Arup Chattopadhyay , Supratim Jana

In this paper, we investigate the complex symmetric structure of generalized weighted composition operators $D_{m,\psi,\varphi}$ on the weighted Hardy space $H^2(\beta)$. We obtain explicit conditions for $ D_{m,\psi,\varphi}$ to be complex…

Functional Analysis · Mathematics 2022-04-25 Lian Hu , Songxiao Li , Rong Yang

We characterize the (essentially) decreasing sequences of positive numbers $\beta$ = ($\beta$ n) for which all composition operators on H 2 ($\beta$) are bounded, where H 2 ($\beta$) is the space of analytic functions f in the unit disk…

Functional Analysis · Mathematics 2022-03-22 Pascal Lefèvre , Daniel Li , Hervé Queffélec , Luis Rodríguez-Piazza

We observe that local embedding problems for certain Hardy and Bergman spaces of Dirichlet series are equivalent to boundedness of a class of composition operators. Following this, we perform a careful study of such composition operators…

Complex Variables · Mathematics 2019-11-05 Frédéric Bayart , Ole Fredrik Brevig

We investigate composition operators on Hardy-Orlicz spaces when the Orlicz function $\Psi$ grows rapidly: compactness, weak compactness, to be $p$-summing, order bounded,..., and show how these notions behave according to the growth of…

Functional Analysis · Mathematics 2007-05-23 Pascal Lefèvre , Daniel Li , Hervé Queffélec , Luis Rodriguez-Piazza

We give examples of results on composition operators connected with lens maps. The first two concern the approximation numbers of those operators acting on the usual Hardy space $H^2$. The last ones are connected with Hardy-Orlicz and…

Functional Analysis · Mathematics 2012-01-04 Pascal Lefèvre , Daniel Li , Hervé Queffélec , Luis Rodriguez-Piazza

We characterize the space of multipliers from the Hardy space of Dirichlet series $\mathcal H_p$ into $\mathcal H_q$ for every $1 \leq p,q \leq \infty$. For a fixed Dirichlet series, we also investigate some structural properties of its…

Complex Variables · Mathematics 2022-05-18 Tomás Fernandez Vidal , Daniel Galicer , Pablo Sevilla-Peris

Let $\varphi: B_d\to\mathbb{D}$, $d\ge 1$, be a holomorphic function, where $B_d$ denotes the open unit ball of $\mathbb{C}^d$ and $\mathbb{D}= B_1$. Let $\Theta: \mathbb{D} \to \mathbb{D}$ be an inner function and let $K^p_\Theta$ denote…

Complex Variables · Mathematics 2026-01-14 Evgueni Doubtsov

In this paper we study the embedding problem of an operator into a strongly continuous semigroup. We obtain characterizations for some classes of operators, namely composition operators and analytic Toeplitz operators on the Hardy space…

Functional Analysis · Mathematics 2025-02-19 Isabelle Chalendar , Romain Lebreton

In this paper, we establish a compactness criterion for the composition-differentiation operator \( D_\Phi \) in terms of a decay condition of the mean counting function at the boundary of a half-plane. We provide a sufficient condition of…

Functional Analysis · Mathematics 2025-04-29 Vasudevarao Allu , Dipon Kumar Mondal