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Variational sparsity regularization based on $\ell^1$-norms and other nonlinear functionals has gained enormous attention recently, both with respect to its applications and its mathematical analysis. A focus in regularization theory has…

Numerical Analysis · Mathematics 2015-06-11 Martin Burger , Jens Flemming , Bernd Hofmann

The Tikhonov regularization of linear ill-posed problems with an $\ell^1$ penalty is considered. We recall results for linear convergence rates and results on exact recovery of the support. Moreover, we derive conditions for exact support…

Functional Analysis · Mathematics 2015-05-18 Dirk A. Lorenz , Stefan Schiffler , Dennis Trede

The convergence rates results in $\ell^1$-regularization when the sparsity assumption is narrowly missed, presented by Burger et al. (2013 Inverse Problems 29 025013), are based on a crucial condition which requires that all basis elements…

Numerical Analysis · Mathematics 2015-08-05 Stephan W. Anzengruber , Bernd Hofmann , Ronny Ramlau

We consider the stable approximation of sparse solutions to non-linear operator equations by means of Tikhonov regularization with a subquadratic penalty term. Imposing certain assumptions, which for a linear operator are equivalent to the…

Functional Analysis · Mathematics 2009-12-06 Markus Grasmair , Markus Haltmeier , Otmar Scherzer

In $\ell^1$-regularization, which is an important tool in signal and image processing, one usually is concerned with signals and images having a sparse representation in some suitable basis, e.g. in a wavelet basis. Many results on…

Optimization and Control · Mathematics 2018-09-28 Jens Flemming , Bernd Hofmann , Ivan Veselic

Measuring the error by an l^1-norm, we analyze under sparsity assumptions an l^0-regularization approach, where the penalty in the Tikhonov functional is complemented by a general stabilizing convex functional. In this context, ill-posed…

Numerical Analysis · Mathematics 2018-10-23 Wei Wang , Shuai Lu , Bernd Hofmann , Jin Cheng

We show that the convergence rate of $\ell^1$-regularization for linear ill-posed equations is always $O(\delta)$ if the exact solution is sparse and if the considered operator is injective and weak*-to-weak continuous. Under the same…

Functional Analysis · Mathematics 2017-01-16 Jens Flemming , Daniel Gerth

This paper deals with Tikhonov regularization for linear and nonlinear ill-posed operator equations with wavelet Besov norm penalties. We focus on $B^0_{p,1}$ penalty terms which yield estimators that are sparse with respect to a wavelet…

Numerical Analysis · Mathematics 2019-09-04 Thorsten Hohage , Philip Miller

The $\ell_{1\text{-}2}$ regularization method has a strong sparsity promoting capability in approaching sparse solutions of linear inverse problems and gained successful applications in various mathematics and applied science fields. This…

Optimization and Control · Mathematics 2026-03-04 Yaohua Hu , Hao Wang , Xiaoqi Yang

Sparsity promoting regularization is an important technique for signal reconstruction and several other ill-posed problems. Theoretical investigation typically bases on the assumption that the unknown solution has a sparse representation…

Numerical Analysis · Mathematics 2013-11-11 Jens Flemming , Markus Hegland

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

Tikhonov regularization involves minimizing the combination of a data discrepancy term and a regularizing term, and is the standard approach for solving inverse problems. The use of non-convex regularizers, such as those defined by trained…

Optimization and Control · Mathematics 2023-02-20 Daniel Obmann , Markus Haltmeier

In this paper we consider convex Tikhonov regularisation for the solution of linear operator equations on Hilbert spaces. We show that standard fractional source conditions can be employed in order to derive convergence rates in terms of…

Optimization and Control · Mathematics 2020-02-24 Markus Grasmair

This work deals with a regularization method enforcing solution sparsity of linear ill-posed problems by appropriate discretization in the image space. Namely, we formulate the so called least error method in an $\ell^1$ setting and perform…

Numerical Analysis · Mathematics 2016-08-03 Kristian Bredies , Barbara Kaltenbacher , Elena Resmerita

For the Tikhonov regularization of ill-posed nonlinear operator equations, convergence is studied in a Hilbert scale setting. We include the case of oversmoothing penalty terms, which means that the exact solution does not belong to the…

Numerical Analysis · Mathematics 2020-02-03 Bernd Hofmann , Robert Plato

We present a new approach to convergence rate results for variational regularization. Avoiding Bregman distances and using image space approximation rates as source conditions we prove a nearly minimax theorem showing that the modulus of…

Numerical Analysis · Mathematics 2021-07-07 Philip Miller

Convergence rates in spectral regularization methods quantify the approximation error in inverse problems as a function of the noise level or the number of sampling points. Classical strong convergence rate results typically rely on source…

Numerical Analysis · Mathematics 2025-12-05 Sabrina Guastavino , Gabriele Santin , Francesco Marchetti , Federico Benvenuto

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

We study Tikhonov regularization for possibly nonlinear inverse problems with weighted $\ell^1$-penalization. The forward operator, mapping from a sequence space to an arbitrary Banach space, typically an $L^2$-space, is assumed to satisfy…

Numerical Analysis · Mathematics 2021-10-19 Philip Miller , Thorsten Hohage

We study the application of Tikhonov regularization to ill-posed nonlinear operator equations. The objective of this work is to prove low order convergence rates for the discrepancy principle under low order source conditions of logarithmic…

Numerical Analysis · Mathematics 2023-05-02 Chantal Klinkhammer , Robert Plato
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