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We study the closure in the Hardy space or the disk algebra of algebras generated by two bounded functions, of which one is a finite Blaschke product. We give necessary and sufficient conditions for density or finite codimension of such…

Complex Variables · Mathematics 2007-05-23 Michael I. Stessin , Pascal J. Thomas

We show that the same similarity characterization obtained for Cowen-Douglas operators to the backward shift operators on reproducing kernel Hilbert spaces with analytic kernels can be used to describe similarity in the Dirichlet space…

Functional Analysis · Mathematics 2013-07-15 Hyun-Kyoung Kwon

Given a densely defined and closed operator $A$ acting on a complex Hilbert space $\mathcal{H}$, we establish a one-to-one correspondence between its closed extensions and subspaces $\mathfrak{M}\subset\mathcal{D}(A^*)$, that are closed…

Functional Analysis · Mathematics 2018-10-12 Christoph Fischbacher

Generalizing previous work of Iwaniec, Luo, and Sarnak (2000), we use information from one-level density theorems to estimate the proportion of non-vanishing of $L$-functions in a family at a low-lying height on the critical line (measured…

Number Theory · Mathematics 2022-10-17 Emanuel Carneiro , Andrés Chirre , Micah B. Milinovich

This paper is a follow-up contribution to our work [20] where we discussed some invariant subspace results for contractions on Hilbert spaces. Here we extend the results of [20] to the context of n-tuples of bounded linear operators on…

Functional Analysis · Mathematics 2015-02-20 Jaydeb Sarkar

Using Zeilberger generating function formula for the values of a discrete analytic function in a quadrant we make connections with the theory of structured reproducing kernel spaces, structured matrices and a generalized moment problem. An…

Complex Variables · Mathematics 2022-03-28 Daniel Alpay , Fabrizio Colombo , Kamal Diki , Irene Sabadini , Dan Volok

We study multivariate integration and approximation for functions belonging to a weighted reproducing kernel Hilbert space based on half-period cosine functions in the worst-case setting. The weights in the norm of the function space depend…

Numerical Analysis · Mathematics 2015-11-23 Christian Irrgeher , Peter Kritzer , Friedrich Pillichshammer

We study reproducing kernel Hilbert spaces introduced as ranges of generalized Ces\`aro-Hardy operators, in one real variable and in one complex variable. Such spaces can be seen as formed by absolutely continuous functions on the positive…

Functional Analysis · Mathematics 2024-01-30 José E. Galé , Pedro J. Miana , Luis Sánchez--Lajustici

We generalize several results on Toeplitz operators over reflexive, standard weighted Fock spaces $F_t^p$ to the non-reflexive cases $p = 1, \infty$. Among these results are the characterization of compactness and the Fredholm property of…

Functional Analysis · Mathematics 2024-01-11 Robert Fulsche

We study reproducing kernel Hilbert and Pontryagin spaces of slice hyperholomorphic functions which are analogs of the Hilbert spaces of analytic functions introduced by de Branges and Rovnyak. In the first part of the paper we focus on the…

Functional Analysis · Mathematics 2012-03-02 Daniel Alpay , Fabrizio Colombo , Irene Sabadini

We analyze the notion of reproducing pair of weakly measurable functions, which generalizes that of continuous frame. We show, in particular, that each reproducing pair generates two Hilbert spaces, conjugate dual to each other. Several…

Functional Analysis · Mathematics 2016-03-09 Jean-Pierre Antoine , Michael Speckbacher , Camillo Trapani

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 2012-09-18 Joseph A. Ball , Vladimir Bolotnikov

Let $T$ be a $C_0$--contraction on a separable Hilbert space. We assume that $I_H-T^*T$ is compact. For a function $f$ holomorphic in the unit disk $\DD$ and continuous on $\bar\DD$, we show that $f(T)$ is compact if and only if $f$…

Functional Analysis · Mathematics 2008-09-19 Karim Kellay , Mohamed Zarrabi

We consider the space of real-valued continuously differentiable functions on a compact subset of a euclidean space. We characterize the completeness of this space and prove that the space of restrictions of continuously differentiable…

Classical Analysis and ODEs · Mathematics 2020-06-18 Leonhard Frerick , Laurent Loosveldt , Jochen Wengenroth

This paper addresses the problem of regression to reconstruct functions, which are observed with superimposed errors at random locations. We address the problem in reproducing kernel Hilbert spaces. It is demonstrated that the estimator,…

Statistics Theory · Mathematics 2021-08-17 Paul Dommel , Alois Pichler

It is shown that the property of being bounded below (having closed range) of weighted composition operators on Hardy and Bergman spaces can be tested by their action on a set of simple test functions, including reproducing kernels. The…

Functional Analysis · Mathematics 2019-02-26 Isabelle Chalendar , Jonathan R. Partington

Pick spaces are a class of reproducing kernel Hilbert spaces that generalize the classical Hardy space and the Drury--Arveson reproducing kernel spaces. We give characterizations of certain contractively included subspaces of Pick spaces.…

Functional Analysis · Mathematics 2013-05-30 Chafiq Benhida , Dan Timotin

We present an approach to defining Hilbert spaces of functions depending on infinitely many variables or parameters, with emphasis on a weighted tensor product construction based on stable space splittings, The construction has been used in…

Numerical Analysis · Mathematics 2016-07-21 Michael Griebel , Peter Oswald

We consider two-variable model spaces associated to rational inner functions $\Theta$ on the bidisk, which always possess canonical $z_2$-invariant subspaces $\mathcal{S}_2.$ A particularly interesting compression of the shift is the…

Complex Variables · Mathematics 2017-02-20 Kelly Bickel , Pamela Gorkin

Some fixed point results are given for a class of functional contractions over partial metric spaces. These extend some contributions in the area due to Ilic et al [Math. Comput. Modelling, 55 (2012), 801-809].

General Topology · Mathematics 2012-03-27 Mihai Turinici