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In this article, the convergence of the often used iterative soft-thresholding algorithm for the solution of linear operator equations in infinite dimensional Hilbert spaces is analyzed in detail. We formulate the algorithm in the framework of generalized gradient methods and present a new convergence analysis. The analysis bases on new techniques like the… (More)

- Kanglin Chen, Dirk A. Lorenz
- Journal of Mathematical Imaging and Vision
- 2011

The problem of the generation of an intermediate image between two given images in an image sequence is considered. The problem is formulated as an optimal control problem governed by a transport equation. This approach bears similarities with the Horn & Schunck method for optical flow calculation but in fact the model is quite different. The images are… (More)

- Kristian Bredies, Dirk A. Lorenz, Peter Maass
- Comp. Opt. and Appl.
- 2009

- Kristian Bredies, Dirk A. Lorenz, Stefan Reiterer
- J. Optimization Theory and Applications
- 2015

The consecutive numbering of the publications is determined by their chronological order. The aim of this preprint series is to make new research rapidly available for scientific discussion. Therefore, the responsibility for the contents is solely due to the authors. The publications will be distributed by the authors. Abstract Numerical algorithms for a… (More)

- L Denis, D A Lorenz, D Trede
- 2009

The orthogonal matching pursuit (OMP) is a greedy algorithm to solve sparse approximation problems. Sufficient conditions for exact recovery are known with and without noise. In this paper we investigate the applicability of the OMP for the solution of ill-posed inverse problems in general and in particular for two deconvolution examples from mass… (More)

- Kristian Bredies, Dirk A. Lorenz
- SIAM J. Scientific Computing
- 2008

A new iterative algorithm for the solution of minimization problems in infinite-dimensional Hilbert spaces which involve sparsity constraints in form of p-penalties is proposed. In contrast to the well-known algorithm considered by Daubechies, Defrise and De Mol, it uses hard instead of soft shrinkage. It is shown that the hard shrinkage algorithm is a… (More)

- Jan Lorenz, Dirk A. Lorenz, +6 authors Roger Waldeck
- 2007

This thesis is about dynamical systems of agents which perform repeated averaging under bounded confidence. It contributes to questions of their modeling, mathematical analysis and simulation. Modeling. The main modeling issue is continuous opinion dynamics. This includes dynamics of agents in a political opinion space as well as dynamics of collective… (More)

- Jan Lorenz, Dirk A. Lorenz
- IEEE Trans. Automat. Contr.
- 2010

A new theorem on conditions for convergence to consensus of a multiagent time-dependent time-discrete dynamical system is presented. The theorem is build up on the notion of averaging maps. We compare this theorem to Moreau's Theorem and his proposed set-valued Lyapunov theory (IEEE Transactions on Automatic Control, vol. 50, no. 2, 2005). We give examples… (More)

- Dirk A. Lorenz
- 2008

This paper addresses the regularization by sparsity constraints by means of weighted ℓ p penalties for 0 ≤ p ≤ 2. For 1 ≤ p ≤ 2 special attention is payed to convergence rates in norm and to source conditions. As main results it is proven that one gets a convergence rate of √ δ in the 2-norm for 1 < p ≤ 2 and in the 1-norm for p = 1 as soon as the unknown… (More)

- K. Bredies, D. A. Lorenz, Kristian Bredies, Dirk A. Lorenz
- 2009

The consecutive numbering of the publications is determined by their chronological order. The aim of this preprint series is to make new research rapidly available for scientific discussion. Therefore, the responsibility for the contents is solely due to the authors. The publications will be distributed by the authors. Abstract We consider regularization of… (More)