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We study weak solutions to nonlocal equations governed by integrodifferential operators. Solutions are defined with the help of symmetric nonlocal bilinear forms. Throughout this work, our main emphasis is on operators with general,…

Analysis of PDEs · Mathematics 2020-03-25 Bartlomiej Dyda , Moritz Kassmann

This paper studies the learning of linear operators between infinite-dimensional Hilbert spaces. The training data comprises pairs of random input vectors in a Hilbert space and their noisy images under an unknown self-adjoint linear…

Statistics Theory · Mathematics 2023-05-12 Maarten V. de Hoop , Nikola B. Kovachki , Nicholas H. Nelsen , Andrew M. Stuart

This paper considers a networked system with a finite number of users and supposes that each user tries to minimize its own private objective function over its own private constraint set. It is assumed that each user's constraint set can be…

Optimization and Control · Mathematics 2015-10-22 Hideaki Iiduka

Firstly, we invoke the weak convergence (resp. strong convergence) of translated basic methods involving nonexpansive operators to establish the weak convergence (resp. strong convergence) of the associated method with both perturbation and…

Optimization and Control · Mathematics 2022-03-29 Hui Ouyang

In this paper we introduce and study a class of structured set-valued operators which we call union averaged nonexpansive. At each point in their domain, the value of such an operator can be expressed as a finite union of single-valued…

Optimization and Control · Mathematics 2020-04-06 Minh N. Dao , Matthew K. Tam

A quasi-product on the normed space is defined. In addition, the notions of the eigenvectors of a linear operator can be extended for the nonlinear operator. Based on the quasi-product and the generalized eigenvectors, the spectral theorems…

Functional Analysis · Mathematics 2020-02-18 Wen Hsiang Wei

Our focus is on the stable approximate solution of linear operator equations based on noisy data by using $\ell^1$-regularization as a sparsity-enforcing version of Tikhonov regularization. We summarize recent results on situations where…

Functional Analysis · Mathematics 2017-11-27 Daniel Gerth , Bernd Hofmann

Variational regularization and the quasisolutions method are justified for unbounded closed, possibly nonlinear, operators. The argument is quite simple and yields general results.

Mathematical Physics · Physics 2007-05-23 A. G. Ramm

We in this paper study the nonexpansive operators equipped with arbitrary metric and investigate the connections between firm nonexpansiveness, cocoerciveness and averagedness. The convergence of the associated fixed-point iterations is…

Optimization and Control · Mathematics 2022-10-11 Feng Xue

We prove boundedness and regularity estimates for weak solutions to a class of linear nonlocal equations involving integro-differential operators with almost no order of differentiability. In particular, we show that bounded weak solutions…

Analysis of PDEs · Mathematics 2025-03-04 Sven Jarohs , Moritz Kassmann , Tobias Weth

Given $N\ge2$ closed subspaces $M_1,\dotsc, M_N$ of a Hilbert space $X$, let $P_k$ denote the orthogonal projection onto $M_k$, $1\le k\le N$. It is known that the sequence $(x_n)$, defined recursively by $x_0=x$ and $x_{n+1}=P_N\cdots…

Functional Analysis · Mathematics 2019-02-14 Catalin Badea , David Seifert

Averaging certain class of quasiperiodic monotone operators can be simplified to the periodic homogenization setting by mapping the original quasiperiodic structure onto a periodic structure in a higher dimensional space using cut-and…

Analysis of PDEs · Mathematics 2023-06-21 Niklas Wellander , Sebastien Guenneau , Elena Cherkaev

In this paper we consider a problem of the similarity of complex symmetric operators to perturbations of restrictions of normal operators. For a subclass of cyclic complex symmetric operators in a finite-dimensional Hilbert space we prove…

Functional Analysis · Mathematics 2021-06-29 Sergey M. Zagorodnyuk

Continuing the study initiated in our earlier article [7], this paper aims to characterize various continuity properties of nonlinear composition operators acting on some sequence spaces, giving special attention to the space of sequences…

Functional Analysis · Mathematics 2025-05-13 Daria Bugajewska , Piotr Kasprzak

Iterative algorithms are fundamental tools for approximating fixed-points of nonexpansive operators in real Hilbert spaces. Among them, Krasnosel'ski\u{\i}--Mann iteration and Halpern iteration are two widely used schemes. In this work, we…

Optimization and Control · Mathematics 2026-02-20 Yifan Bai , Yantao Li , Jian Yu , Jingwei Liang

This paper establishes several new inequalities for the $A$-norm and $A$-numerical radius of operator sums in semi-Hilbertian spaces, significantly advancing the existing theory. We present two fundamental refinements of the generalized…

Functional Analysis · Mathematics 2025-07-09 M. H. M. Rashid

We consider the split convex feasibility problem in a fixed point setting. Motivated by the well-known CQ-method of Byrne (2002), we define an abstract andweber transform which applies to more general operators than the metric projection.…

Optimization and Control · Mathematics 2018-12-19 Andrzej Cegielski , Simeon Reich , Rafał Zalas

We investigate the asymptotic behavior of Halpern-type iterations applied to quasi-nonexpansive operators arising in best approximation problems over the intersection of finitely many closed convex sets in $\mathbb{R}^n$. Assuming a local…

Optimization and Control · Mathematics 2026-05-29 Pablo Barros , Vincent Guigues , Roger Behling , Luiz-Rafael Santos

We give a brief account on a basic result (Lemma \ref{lem2}) which is a very useful tool in proving various convergence theorems in the framework of the iterative approximation of fixed points of demicontractive mappings in Hilbert spaces.…

General Mathematics · Mathematics 2024-04-10 Vasile Berinde

Monotone operators, especially in the form of subdifferential operators, are of basic importance in optimization. It is well known since Minty, Rockafellar, and Bertsekas-Eckstein that in Hilbert space, monotone operators can be understood…

Functional Analysis · Mathematics 2008-10-22 Heinz H. Bauschke , Xianfu Wang , Liangjin Yao