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Regularization of nonlinear ill-posed problems by exponentialintegrators

Published online by Cambridge University Press:  08 July 2009

Marlis Hochbruck ,
Michael Hönig  and
Alexander Ostermann
Marlis Hochbruck
Affiliation:
Mathematisches Institut, Heinrich-Heine Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany. marlis@am.uni-duesseldorf.de; hoenig@am.uni-duesseldorf.de
Michael Hönig
Affiliation:
Mathematisches Institut, Heinrich-Heine Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany. marlis@am.uni-duesseldorf.de; hoenig@am.uni-duesseldorf.de
Alexander Ostermann
Affiliation:
Institut für Mathematik, Universität Innsbruck, Technikerstraße 13, 6020 Innsbruck, Austria. alexander.ostermann@uibk.ac.at
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Abstract

The numerical solution of ill-posed problems requires suitable regularization techniques. One possible option is to consider time integration methods to solve the Showalter differential equation numerically. The stopping time of the numerical integrator corresponds to the regularization parameter. A number of well-known regularization methods such as the Landweber iteration or the Levenberg-Marquardt method can be interpreted as variants of the Euler method for solving the Showalter differential equation. Motivated by an analysis of the regularization properties of the exact solution of this equation presented by [U. Tautenhahn, Inverse Problems10 (1994) 1405–1418], we consider a variant of the exponential Euler method for solving the Showalter ordinary differential equation. We discuss a suitable discrepancy principle for selecting the step sizes within the numerical method and we review the convergence properties of [U. Tautenhahn, Inverse Problems10 (1994) 1405–1418], and of our discrete version [M. Hochbruck et al., Technical Report (2008)]. Finally, we present numerical experiments which show that this method can be efficiently implemented by using Krylov subspace methods to approximate the product of a matrix function with a vector.

Keywords

Nonlinear ill-posed problemsasymptotic regularizationexponential integratorsvariable step sizesconvergenceoptimal convergence rates.
Type
Research Article
Information
ESAIM: Mathematical Modelling and Numerical Analysis , Volume 43 , Issue 4: Special issue on Numerical ODEs today , July 2009 , pp. 709 - 720
Copyright
© EDP Sciences, SMAI, 2009

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