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When solving rank-deficient or discrete ill-posed problems by regularization methods, the choice of the regularization parameter is crucial. It is also of interest, the regularization norm used in the selection of the solution. In this…

Numerical Analysis · Mathematics 2024-10-30 Ibrahima Dione

We propose and analyze a posteriori error estimates for a control-constrained optimal control problem with bang-bang solutions. We consider a solution strategy based on the variational approach, where the control variable is not…

Optimization and Control · Mathematics 2025-05-26 Francisco Fuica

The Tikhonov-Phillips method is widely used for regularizing ill-posed inverse problems mainly due to the simplicity of its formulation as an optimization problem. The use of different penalizers in the functionals associated to the…

Functional Analysis · Mathematics 2011-08-23 Gisela L. Mazzieri , Ruben D. Spies , Karina G. Temperini

Most of the literature on the solution of linear ill-posed operator equations, or their discretization, focuses only on the infinite-dimensional setting or only on the solution of the algebraic linear system of equations obtained by…

Numerical Analysis · Mathematics 2018-12-05 Ronny Ramlau , Lothar Reichel

In this contribution, we are concerned with model order reduction in the context of iterative regularization methods for the solution of inverse problems arising from parameter identification in elliptic partial differential equations. Such…

Numerical Analysis · Mathematics 2024-10-14 Michael Kartmann , Tim Keil , Mario Ohlberger , Stefan Volkwein , Barbara Kaltenbacher

This paper focuses on the regularization of backward time-fractional diffusion problem on unbounded domain. This problem is well-known to be ill-posed, whence the need of a regularization method in order to recover stable approximate…

Numerical Analysis · Mathematics 2022-01-03 Walter Simo Tao Lee

This paper provides a new algorithm for solving inverse problems, based on the minimization of the $L^2$ norm and on the control of the Total Variation. It consists in relaxing the role of the Total Variation in the classical Total…

Computer Vision and Pattern Recognition · Computer Science 2011-10-17 Qiyu Jin , Ion Grama , Quansheng Liu

We consider joint Tikhonov- and Lavrentiev-regularization of control problems with pointwise control- and state-constraints. We derive error estimates for the error which is introduced by the Tikhonov regularization. With the help of this…

Optimization and Control · Mathematics 2010-10-26 Dirk A. Lorenz , Arnd Rösch

In this paper we study adaptive discretization of the iteratively regularized Gauss-Newton method IRGNM with an a posteriori (discrepancy principle) choice of the regularization parameter in each Newton step and of the stopping index. We…

Numerical Analysis · Mathematics 2015-06-17 Barbara Kaltenbacher , Alana Kirchner , Slobodan Veljovi\' c

We consider a regularization concept for the solution of ill--posed operator equations, where the operator is composed of a continuous and a discontinuous operator. A particular application is level set regularization, where we develop a…

Numerical Analysis · Mathematics 2020-11-16 F. Frühauf , O. Scherzer , A. Leitao

We consider the strongly convergent modified versions of the Krasnosel'ski\u{\i}-Mann, the forward-backward and the Douglas-Rachford algorithms with Tikhonov regularization terms, introduced by Radu Bo\c{t}, Ern\"{o} Csetnek and Dennis…

Functional Analysis · Mathematics 2021-01-05 Bruno Dinis , Pedro Pinto

The a posteriori error estimates are studied for a class of nonlinear stead-state Poisson-Nernst-Planck equations, which are a coupled system consisting of the Nernst-Planck equation and the Poisson equation. Both the global upper bounds…

Numerical Analysis · Mathematics 2020-01-10 Ying Yang , Ruigang Shen , Mingjuan Fang , Shi Shu

Regularization techniques are necessary to compute meaningful solutions to discrete ill-posed inverse problems. The well-known 2-norm Tikhonov regularization method equipped with a discretization of the gradient operator as regularization…

Numerical Analysis · Mathematics 2024-06-05 Silvia Gazzola , Ali Gholami

Regularization plays a pivotal role in ill-posed machine learning and inverse problems. However, the fundamental comparative analysis of various regularization norms remains open. We establish a small noise analysis framework to assess the…

Machine Learning · Statistics 2024-09-05 Quanjun Lang , Fei Lu

Regularization is a core component of modern inverse problems, as it helps establish the well-posedness of the solution of interest. Popular regularization approaches include variational regularization and iterative regularization. The…

Optimization and Control · Mathematics 2025-08-08 Jie Gao , Cesare Molinari , Silvia Villa , Jingwei Liang

In this paper, we propose a generalized successive approximation method (SAM), called invariantly admissible policy iteration (PI), for finding the solution to a class of input-affine nonlinear optimal control problems by iterations. Unlike…

Optimization and Control · Mathematics 2014-05-28 Jae Youg Lee , Jin Bae Park , Yoon Ho Choi

We investigate a level-set type method for solving ill-posed problems, with the assumption that the solutions are piecewise, but not necessarily constant functions with unknown level sets and unknown level values. In order to get stable…

Numerical Analysis · Mathematics 2012-10-30 Adriano De Cezaro

Convergence rates results for Tikhonov regularization of nonlinear ill-posed operator equations in abstract function spaces require the handling of both smoothness conditions imposed on the solution and structural conditions expressing the…

Numerical Analysis · Mathematics 2009-09-29 Radu Ioan Bot , Bernd Hofmann

We present a regularization method to approach a solution of the pessimistic formulation of ill -posed bilevel problems . This allows to overcome the difficulty arising from the non uniqueness of the lower level problems solutions and…

Optimization and Control · Mathematics 2016-08-16 Maïtine Bergounioux , Mounir Haddou

This paper is a close follow-up of Kaltenbacher and Tomba 2013 and Jin 2012, where Newton-Landweber iterations have been shown to converge either (unconditionally) without rates or (under an additional regularity assumption) with rates. The…

Numerical Analysis · Mathematics 2014-08-22 Barbara Kaltenbacher , Ivan Tomba