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Using Landweber iteration to quantify source conditions – a numerical study

  • Daniel Gerth EMAIL logo

Abstract

Source conditions of the type x((AA)μ) are a standard assumption in the theory of inverse problems to show convergence rates of regularized solutions as the noise in the data goes to zero. Unfortunately, it is rarely possible to verify these conditions in practice, rendering data-independent parameter choice rules unfeasible. In this paper we show that such a source condition implies a Kurdyka–Łojasiewicz inequality with certain parameters depending on μ. While the converse implication is unclear from a theoretical point of view, we propose an algorithm which represents a first attempt that allows to approximate the value of μ numerically. It is based on combining the Landweber iteration with the Kurdyka–Łojasiewicz inequality. We conduct several numerical experiments to demonstrate the potential and limitations of the current method. We also show that the source condition implies a lower bound on the convergence rate which is of optimal order and observable without the knowledge of μ.

MSC 2010: 65J22; 49N45

Award Identifier / Grant number: HO 1454/10-1

Funding statement: Research supported by Deutsche Forschungsgemeinschaft (DFG-grant HO 1454/10-1).

Acknowledgements

The author thanks the anonymous referees for their comments that helped to improve this paper. The helpful comments and discussions with Bernd Hofmann (TU Chemnitz) and Oliver Ernst (TU Chemnitz) are gratefully acknowledged.

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Received: 2018-01-15
Revised: 2018-10-29
Accepted: 2018-11-02
Published Online: 2018-11-21
Published in Print: 2019-06-01

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