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We consider linear ill-conditioned operator equations in a Hilbert space setting. Motivated by the aggregation method, we consider approximate solutions constructed from linear combinations of Tikhonov regularization, which amounts to…

Numerical Analysis · Mathematics 2023-06-07 Stefan Kindermann , Werner Zellinger

Regularizing a linear ill-posed operator equation can be achieved by manipulating the spectrum of the operator's pseudo-inverse. Tikhonov regularization and spectral cutoff are well-known techniques within this category. This paper…

Numerical Analysis · Mathematics 2026-02-11 Martin Sæbye Carøe , Mirza Karamehmedović , Pierre Maréchal

We introduce a neural network architecture to solve inverse problems linked to a one-dimensional integral operator. This architecture is built by unfolding a forward-backward algorithm derived from the minimization of an objective function…

Optimization and Control · Mathematics 2021-06-01 Emilie Chouzenoux , Cecile Della Valle , Jean-Christophe Pesquet

In this paper we deal with linear inverse problems and convergence rates for Tikhonov regularization. We consider regularization in a scale of Banach spaces, namely the scale of Besov spaces. We show that regularization in Banach scales…

Functional Analysis · Mathematics 2009-11-13 Dirk Lorenz , Dennis Trede

The paper gives a detailed survey of recent results on elliptic problems in Hilbert spaces of generalized smoothness. The latter are the isotropic H\"ormander spaces $H^{s,\varphi}:=B_{2,\mu}$, with $\mu(\xi)=<\xi>^{s}\varphi(<\xi>)$ for…

Functional Analysis · Mathematics 2012-06-27 Vladimir A. Mikhailets , Aleksandr A. Murach

We tackle the problem of building adaptive estimation procedures for ill-posed inverse problems. For general regularization methods depending on tuning parameters, we construct a penalized method that selects the optimal smoothing sequence…

Statistics Theory · Mathematics 2008-07-31 Jean-Michel Loubes , Carenne Ludeña

Solutions of partial differential equations can often be written as surface integrals having a kernel related to a singular fundamental solution. Special methods are needed to evaluate the integral accurately at points on or near the…

Numerical Analysis · Mathematics 2025-10-16 J. Thomas Beale , Svetlana Tlupova

The standard approach for dealing with the ill-posedness of the training problem in machine learning and/or the reconstruction of a signal from a limited number of measurements is regularization. The method is applicable whenever the…

Optimization and Control · Mathematics 2020-07-13 Michael Unser

We consider perturbed nonlinear ill-posed equations in Hilbert spaces, with operators that are monotone on a given closed convex subset. A simple stable approach is Lavrentiev regularization, but existence of solutions of the regularized…

Numerical Analysis · Mathematics 2018-06-05 Robert Plato , Bernd Hofmann

A learning approach for determining which operator from a class of nonlocal operators is optimal for the regularization of an inverse problem is investigated. The considered class of nonlocal operators is motivated by the use of squared…

Optimization and Control · Mathematics 2021-07-15 Gernot Holler , Karl Kunisch

We analyse the Krylov solvability of inverse linear problems on Hilbert space $\mathcal{H}$ where the underlying operator is compact and normal. Krylov solvability is an important feature of inverse linear problems that has profound…

Functional Analysis · Mathematics 2023-09-28 Noe Angelo Caruso

A convergent iterative process is constructed for solving any solvable linear equation in a Hilbert space.

Numerical Analysis · Mathematics 2007-05-23 A. G. Ramm

We suggest an approach for description of integrable cases of the Abel equations. It is based on increasing of the order of equations up to the second one and using equivalence transformations for the corresponding second-order ordinary…

Exactly Solvable and Integrable Systems · Physics 2007-05-23 Vyacheslav M. Boyko

Iterative regularization exploits the implicit bias of an optimization algorithm to regularize ill-posed problems. Constructing algorithms with such built-in regularization mechanisms is a classic challenge in inverse problems but also in…

Optimization and Control · Mathematics 2022-02-02 Cesare Molinari , Mathurin Massias , Lorenzo Rosasco , Silvia Villa

Many problems in Science and Engineering give rise to linear integral equations of the first kind with a smooth kernel. Discretization of the integral operator yields a matrix, whose singular values cluster at the origin. We describe the…

Numerical Analysis · Mathematics 2022-04-13 Thomas Mach , Lothar Reichel , Marc Van Barel

Connected with the rise of interest in inverse problems is the development and analysis of regularization methods, which are a necessity due to the ill-posedness of inverse problems. Tikhonov-type regularization methods are very popular in…

Numerical Analysis · Mathematics 2021-03-16 Abinash Nayak

This paper addresses Tikhonov like regularization methods with convex penalty functionals for solving nonlinear ill-posed operator equations formulated in Banach or, more general, topological spaces. We present an approach for proving…

Numerical Analysis · Mathematics 2009-06-19 Jens Geissler , Bernd Hofmann

In this paper, we apply a new kind of smoothness concept, i.e. H\"older stability estimates for the determination of convergence rates of Tikhonov regularization for linear and non-linear inverse problems in Hilbert spaces. For linear…

Numerical Analysis · Mathematics 2020-11-05 Gaurav Mittal , Ankik Kumar Giri

Conditional stability estimates are a popular tool for the regularization of ill-posed problems. A drawback in particular under nonlinear operators is that additional regularization is needed for obtaining stable approximate solutions if…

Numerical Analysis · Mathematics 2019-05-29 Daniel Gerth , Bernd Hofmann , Christopher Hofmann

We consider abstract operator equations $Fu=y$, where $F$ is a compact linear operator between Hilbert spaces $U$ and $V$, which are function spaces on \emph{closed, finite dimensional Riemannian manifolds}, respectively. This setting is of…

Numerical Analysis · Mathematics 2015-05-28 Nicolas Thorstensen , Otmar Scherzer