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This paper is aimed to prove a quantitative estimate (in terms of the modulus of continuity) for the convergence in the nonlinear version of Korovkin's theorem for sequences of weakly nonlinear and monotone operators defined on spaces of…

Functional Analysis · Mathematics 2024-04-18 Sorin G. Gal , Constantin P. Niculescu

In this article, we obtain hessian estimates for Kolmogorov-Fokker-Planck operators in non-divergence form in several Banach function spaces. Our approach relies on a representation formula and newly developed sparse domination techniques…

Analysis of PDEs · Mathematics 2022-05-31 Abhishek Ghosh , Vivek Tewary

We study the numerical approximation of fractional powers of accretive operators in this paper. Namely, if $A$ is the accretive operator associated with an accretive sesquilinear form $A(\cdot,\cdot)$ defined on a Hilbert space $\mathbb V$…

Numerical Analysis · Mathematics 2016-07-15 Andrea Bonito , Joseph E. Pasciak

In this article, the approximation properties of the Szasz-Mirakjan type operators are studied for the function of two variables, and the rate of convergence of the bivariate operators is determined in terms of total and partial modulus of…

Functional Analysis · Mathematics 2020-05-27 Rishikesh Yadav , Ramakanta Meher , Vishnu Narayan Mishra

In this paper, we investigate Durrmeyer-type generalizations of maximum-minimum neural network operators. The primary objective of this study is to establish the convergence of these operators in the $L^{p}$ norm for functions $f\in…

Numerical Analysis · Mathematics 2026-02-02 Berke Şahin , İsmail Aslan

In this paper, we analyze metrical approximations of functions $F :\Lambda times X \rightarrow Y$ by trigonometric polynomials and $\rho$-periodic type functions, where $\emptyset \neq \Lambda \subseteq {\mathbb R}^{n},$ $X$ and $Y $are…

Functional Analysis · Mathematics 2022-05-19 B. Chaouchi , M. Kostic , D. Velinov

Using results from theory of operators on a Hilbert space, we prove approximation results for matrix-valued holomorphic functions on the unit disc and the unit bidisc. The essential tools are the theory of unitary dilation of a contraction…

Complex Variables · Mathematics 2023-06-27 Daniel Alpay , Tirthankar Bhattacharyya , Abhay Jindal , Poornendu Kumar

Operator learning is the approximation of operators between infinite dimensional Banach spaces using machine learning approaches. While most progress in this area has been driven by variants of deep neural networks such as the Deep Operator…

Machine Learning · Computer Science 2025-09-11 Chunyang Liao , Deanna Needell , Hayden Schaeffer

In this paper, we introduce a new class of positive linear operators that generalize the classical Bernstein operators. Specifically, we construct a sequence of operators that reproduce the logarithmic function $\ln(1+\mu+x)$, with $\mu >…

Functional Analysis · Mathematics 2026-03-13 Laura Angeloni , Danilo Costarelli , Chiara Darielli

We discuss approximation of extremal functions by polynomials in the weighted Bergman spaces $A^p_\alpha$ where $-1 < \alpha < 0$ and $-1 < \alpha < p-2$. We obtain bounds on how close the approximation is to the true extremal function in…

Complex Variables · Mathematics 2017-05-19 Timothy Ferguson

In this paper we deal with the convergence of sequences of positive linear maps to a (not assumed to be linear) isometry on spaces of continuous functions. We obtain generalizations of known Korovkin-type results and provide several…

Functional Analysis · Mathematics 2019-08-09 M. Hosseini , J. J. Font

In a recent article, Dumitru Popa proved an operator version of the Korovkin theorem. We recall the quantitative version of the Korovkin theorem obtained by O. Shisha and B. Mond in 1968. In this paper, we obtain a quantitative estimate for…

Functional Analysis · Mathematics 2024-02-22 V. B. Kiran Kumar , P. C. Vinaya

In this note the Choquet type operators are introduced, in connection to Choquet's theory of integrability with respect to a not necessarily additive set function. Based on their properties, a quantitative estimate for the nonlinear…

Classical Analysis and ODEs · Mathematics 2021-04-14 Sorin G. Gal , Constantin P. Niculescu

In this article we consider means of positive bounded linear operators on a Hilbert space. We present a complete theory that provides a framework which extends the theory of the Karcher mean, its approximating matrix power means, and a…

Functional Analysis · Mathematics 2016-01-27 Miklós Pálfia

Given a set of matrices, modeled as samples of a matrix-valued function, we suggest a method to approximate the underline function using a product approximation operator. This operator extends known approximation methods by exploiting the…

Numerical Analysis · Mathematics 2016-11-15 Nira Dyn , Uri Itai , Nir Sharon

Approximation properties of multivariate Kantorovich-Kotelnikov type operators generated by different band-limited functions are studied. In particular, a wide class of functions with discontinuous Fourier transform is considered. The…

Classical Analysis and ODEs · Mathematics 2018-11-20 Yu. Kolomoitsev , M. Skopina

In this paper, we show that Besov and Triebel-Lizorkin functions can be approximated by a H\"older continuous function both in the Lusin sense and in norm. The results are proven in metric measure spaces for Haj{\l}asz-Besov and…

Functional Analysis · Mathematics 2015-04-13 Toni Heikkinen , Heli Tuominen

Approximating the action of a matrix function $f(\mathbf{A})$ on a vector $\mathbf{b}$ is an increasingly important primitive in machine learning, data science, and statistics, with applications such as sampling high dimensional Gaussians,…

Numerical Analysis · Mathematics 2024-11-07 Noah Amsel , Tyler Chen , Anne Greenbaum , Cameron Musco , Chris Musco

This letter presents an almost sure convergence of the zeroth-order mirror descent algorithm. The algorithm admits non-smooth convex functions and a biased oracle which only provides noisy function value at any desired point. We approximate…

Optimization and Control · Mathematics 2024-07-02 Anik Kumar Paul , Arun D Mahindrakar , Rachel K Kalaimani

In this paper we obtain degree of approximation of functions in Lp by operators associated with their Fourier series using integral modulus of continuity. These results generalize many know results and are proved under less stringent…

Classical Analysis and ODEs · Mathematics 2012-05-29 R. N. Mohapatra , B. Szal