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We establish spectral convergence results of approximations of unbounded non-selfadjoint linear operators with compact resolvents by operators that converge in generalized strong resolvent sense. The aim is to establish general assumptions…

Spectral Theory · Mathematics 2016-04-27 Sabine Bögli

Operator convex functions defined on the positive half-line play a prominent role in the theory of quantum information, where they are used to define quantum $f$-divergences. Such functions admit integral representations in terms of…

Optimization and Control · Mathematics 2023-05-23 Oisín Faust , Hamza Fawzi

We develop a unified second-order parameterized complexity theory for spaces of integrable functions. This generalizes the well-established case of second-order parameterized complexity theory for spaces of continuous functions.…

Computational Complexity · Computer Science 2025-06-16 Aras Bacho , Martin Ziegler

In this paper we introduce a very general setting dealing with the superposition of operators of any positive order and provide a systematic study of them. We also provide examples and counterexamples, as well as characterizing properties…

Analysis of PDEs · Mathematics 2025-10-10 Serena Dipierro , Sven Jarohs , Enrico Valdinoci

The purpose of this paper is to study the approximation of vector valued mappings defined on a subset of a normed space. We investigate Korovkin-type conditions under which a given sequence of linear operators becomes a so-called…

Functional Analysis · Mathematics 2007-05-23 Lorenzo D'Ambrosio

We seek random versions of some classical theorems on complex approximation by polynomials and rational functions, as well as investigate properties of random compact sets in connection to complex approximation.

Complex Variables · Mathematics 2017-09-26 Simon St-Amant , Jérémie Turcotte

In this note a general approach is suggested for comparison of operators. This is done by means of the Fourier transform of a measure. This approach is applied to comparison of approximation properties of various summability methods of the…

Classical Analysis and ODEs · Mathematics 2014-04-23 Roald M. Trigub

We study approximation by arbitrary linear combinations of $n$ translates of a single function of periodic functions. We construct some methods of this approximation for functions in a class induced by the convolution with a given function,…

Numerical Analysis · Mathematics 2017-03-01 Dinh Dũng , Charles A. Micchelli , Vu Nhat Huy

In the present article, we propose the new class positive linear operators, which discrete type depending on a real parameters. These operators are similar to Jain operators but its approximation properties are different then Jain…

Classical Analysis and ODEs · Mathematics 2019-04-19 Prashantkumar Patel

We investigate the rational approximation of fractional powers of unbounded positive operators attainable with a specific integral representation of the operator function. We provide accurate error bounds by exploiting classical results in…

Numerical Analysis · Mathematics 2024-03-19 Lidia Aceto , Paolo Novati

In this paper, we introduce Mellin-Steklov exponential samplingoperators of order $r,r\in\mathbb{N}$, by considering appropriate Mellin-Steklov integrals. We investigate the approximation properties of these operators in continuousbounded…

Functional Analysis · Mathematics 2024-10-15 D Ozer , S Kursun , T Acar

In weighted Orlicz type spaces ${\mathcal S}_{_{\scriptstyle \mathbf p,\,\mu}}$ with a variable summation exponent, the direct and inverse approximation theorems are proved in terms of best approximations of functions and moduli of…

Classical Analysis and ODEs · Mathematics 2020-04-22 Fahreddin G. Abdullayev , Stanislav O. Chaichenko , Meerim Imash kyzy , Andrii L. Shidlich

We study the approximation numbers of weighted composition operators $f\mapsto w\cdot(f\circ\varphi)$ on the Hardy space $H^2$ on the unit disc. For general classes of such operators, upper and lower bounds on their approximation numbers…

Functional Analysis · Mathematics 2017-12-27 Gandalf Lechner , Daniel Li , Hervé Queffélec , Luis Rodríguez-Piazza

In this article, we give a sequence of operators for producing an approximation result. The relation between the rate of approximation of sequence operators including Dunkl variant of exponential function with first and second-order modulus…

Classical Analysis and ODEs · Mathematics 2019-01-28 Sezgin Sucu

Many studies have been conducted on statistical convergence, and it remains an area of active research. Since its introduction, statistical convergence has found applications many fields. Nevertheless, there is a shortage of research…

Functional Analysis · Mathematics 2024-06-14 Erdal Bayram , Mehmet Küçükaslan , Mikail Et , Abdullah Aydın

Some concepts, such as non-compactness measure and condensing operators, defined on metric spaces are extended to uniform spaces. Such extensions allow us to locate, in the context of uniform spaces, some classical results existing in…

General Topology · Mathematics 2015-11-25 Raúl Fierro

Given an operator ideal I, a Banach space E has the I-approximation property if operators on E can be uniformly approximated on compact subsets of E by operators belonging to I. In this paper the I- approximation property is studied in…

Functional Analysis · Mathematics 2010-09-16 Sonia Berrios , Geraldo Botelho

In the present paper, we use a generalised shift operator in order to define a generalised modulus of smoothness. By its means, we define generalised Lipschitz classes of functions, and we give their constructive characteristics.…

Functional Analysis · Mathematics 2014-01-28 Faton M. Berisha , Nimete Sh. Berisha

Generalized translation operators for orthogonal expansions with respect to families of weight functions on the unit ball and on the standard simplex are studied. They are used to define convolution structures and modulus of smoothness for…

Classical Analysis and ODEs · Mathematics 2007-05-23 Yuan Xu

In this paper, we considered the problem of the simultaneous approximation of a function and its derivatives by means of the well-known neural network (NN) operators activated by sigmoidal function. Other than a uniform convergence theorem…

Functional Analysis · Mathematics 2025-02-25 Marco Cantarini , Danilo Costarelli