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We introduce subgradient-based Lavrentiev regularisation of the form \begin{equation*} \mathcal{A}(u) + \alpha \partial \mathcal{R}(u) \ni f^\delta \end{equation*} for linear and nonlinear ill-posed problems with monotone operators…

Optimization and Control · Mathematics 2024-10-01 Markus Grasmair , Fredrik Hildrum

In this note we show that a recent existence result on quasiequilibrium problems, which seems to improve deeply some well-known results, is not correct. We exhibit a counterexample and we furnish a generalization of a lemma about continuous…

Optimization and Control · Mathematics 2015-04-08 Marco Castellani , Massimiliano Giuli

In this work, we investigate a stochastic gradient descent method for solving inverse problems that can be written as systems of linear or nonlinear ill-posed equations in Banach spaces. The method uses only a randomly selected equation at…

Numerical Analysis · Mathematics 2024-09-10 Ruixue Gu , Zhenwu Fu , Bo Han , Hongsun Fu

Although the \emph{residual method}, or \emph{constrained regularization}, is frequently used in applications, a detailed study of its properties is still missing. This sharply contrasts the progress of the theory of Tikhonov…

Optimization and Control · Mathematics 2012-12-06 Markus Grasmair , Markus Haltmeier , Otmar Scherzer

We study the convergence of variationally regularized solutions to linear ill-posed operator equations in Banach spaces as the noise in the right hand side tends to $0$. The rate of this convergence is determined by abstract smoothness…

Numerical Analysis · Mathematics 2018-07-17 Benjamin Sprung , Thorsten Hohage

In this short note, we formulate the convergence rates of the well known Tikhonov regularization scheme for solving the nonlinear ill-posed problems in Banach spaces. For deriving the convergence rates, we employ the novel smoothness…

Numerical Analysis · Mathematics 2022-11-30 Gaurav Mittal , Ankik Kumar Giri

Solving inverse problems \(Ax = y\) is central to a variety of practically important fields such as medical imaging, remote sensing, and non-destructive testing. The most successful and theoretically best-understood method is convex…

Numerical Analysis · Mathematics 2025-09-23 Daniel Obmann , Gyeongha Hwang , Markus Haltmeier

Vector-valued learning, where the output space admits a vector-valued structure, is an important problem that covers a broad family of important domains, e.g. multi-task learning and transfer learning. Using local Rademacher complexity and…

Machine Learning · Computer Science 2023-08-30 Jian Li , Yong Liu , Weiping Wang

The main purpose of this paper is to propose a variance-based Bregman extragradient algorithm with line search for solving stochastic variational inequalities, which is robust with respect an unknown Lipschitz constant. We prove the almost…

Optimization and Control · Mathematics 2022-08-31 Xian-Jun Long , Yue-Hong He , Nan-Jing Huang

We study the last-iterate convergence of variance reduction methods for extragradient (EG) algorithms for a class of variational inequalities satisfying error-bound conditions. Previously, last-iterate linear convergence was only known…

Optimization and Control · Mathematics 2024-01-02 Tianlong Nan , Yuan Gao , Christian Kroer

Tensor-based methods are receiving a growing interest in scientific computing for the numerical solution of problems defined in high dimensional tensor product spaces. A family of methods called Proper Generalized Decompositions methods…

Numerical Analysis · Mathematics 2011-12-02 Antonio Falco , Anthony Nouy

A nonlinear equation in a Banach space is written as a linear equation with a linear operator depending on the unknown solution. This method, which we call a global linearization method, differs essentially from the local linearization…

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

The aim of this paper is to present an extragradient method for variational inequality associated to a point-to-set vector field in Hadamard manifolds and to study its convergence properties. In order to present our method the concept of…

Optimization and Control · Mathematics 2018-04-26 E. E. A. Batista , G. C. Bento , O. P. Ferreira

The Stochastic Extragradient (SEG) method is one of the most popular algorithms for solving min-max optimization and variational inequalities problems (VIP) appearing in various machine learning tasks. However, several important questions…

Optimization and Control · Mathematics 2022-02-23 Eduard Gorbunov , Hugo Berard , Gauthier Gidel , Nicolas Loizou

Data-driven modeling increasingly requires to find a Nash equilibrium in multi-player games, e.g. when training GANs. In this paper, we analyse a new extra-gradient method for Nash equilibrium finding, that performs gradient extrapolations…

We provide a new approach to obtain solutions of certain evolution equations set in a Banach space and equipped with nonlocal boundary conditions. From this approach we derive a family of numerical schemes for the approximation of the…

Numerical Analysis · Mathematics 2024-02-13 Paola Boito , Yuli Eidelman , Luca Gemignani

We consider Tikhonov-type variational regularization of ill-posed linear operator equations in Banach spaces with general convex penalty functionals. Upper bounds for certain error measures expressing the distance between exact and…

Numerical Analysis · Mathematics 2017-12-06 Jens Flemming

In this paper, we firstly prove the existence of the equilibrium for the generalized abstract economy. We apply these results to show the existence of solutions for systems of vector quasi-equilibrium problems with multivalued trifunctions.…

Optimization and Control · Mathematics 2015-07-07 Monica Patriche

Obtaining meaningful solutions for inverse problems has been a major challenge with many applications in science and engineering. Recent machine learning techniques based on proximal and diffusion-based methods have shown promising results.…

Machine Learning · Computer Science 2024-02-08 Moshe Eliasof , Eldad Haber , Eran Treister

Previously unknown estimates of uniform continuity of projection operators in Banach space have been obtained. They can be used in the investigations of approximation methods, in particular, the method of quasisolutions, methods of…

funct-an · Mathematics 2008-02-03 Ya. I. Alber , A. I. Notik