## Regularized Fixed-Point Iterations for Nonlinear Inverse Problems

- In this paper we introduce a derivative-free, iterative method for solving nonlinear ill-posed problems \(Fx=y\), where instead of \(y\) noisy data \(y_\delta\) with \(|| y-y_\delta ||\leq \delta\) are given and \(F:D(F)\subseteq X \rightarrow Y\) is a nonlinear operator between Hilbert spaces \(X\) and \(Y\). This method is defined by splitting the operator \(F\) into a linear part \(A\) and a nonlinear part \(G\), such that \(F=A+G\). Then iterations are organized as \(A u_{k+1}=y_\delta-Gu_k\). In the context of ill-posed problems we consider the situation when \(A\) does not have a bounded inverse, thus each iteration needs to be regularized. Under some conditions on the operators \(A\) and \(G\) we study the behavior of the iteration error. We obtain its stability with respect to the iteration number \(k\) as well as the optimal convergence rate with respect to the noise level \(\delta\), provided that the solution satisfies a generalized source condition. As an example, we consider an inverse problem of initial temperature reconstruction for a nonlinear heat equation, where the nonlinearity appears due to radiation effects. The obtained iteration error in the numerical results has the theoretically expected behavior. The theoretical assumptions are illustrated by a computational experiment.

Author: | S.S. Pereverzyev, R. Pinnau, N. Siedow |
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URN (permanent link): | urn:nbn:de:hbz:386-kluedo-13860 |

Serie (Series number): | Berichte der Arbeitsgruppe Technomathematik (AGTM Report) (262) |

Document Type: | Preprint |

Language of publication: | English |

Year of Completion: | 2005 |

Year of Publication: | 2005 |

Publishing Institute: | Technische Universität Kaiserslautern |

Tag: | derivative-free iterative method ; heat radiation; initial temperature ; nonlinear heat equation ; nonlinear inverse problem ; regularization |

Source: | Preprint Version von gleichnamigen Artikel, der in Inverse Problems, 22 (2006), pp. 1–22 erschienen ist |

Faculties / Organisational entities: | Fachbereich Mathematik |

DDC-Cassification: | 510 Mathematik |

MSC-Classification (mathematics): | 65J15 Equations with nonlinear operators (do not use 65Hxx) |

65J20 Improperly posed problems; regularization | |

80A23 Inverse problems |