Abstract
We consider nonlinear inverse problems described by operator equations in Banach spaces. Assuming conditional stability of the inverse problem, that is, assuming that stability holds on a compact, convex subset of the domain of the operator, we introduce a novel nonlinear projected steepest descent iteration and analyze its convergence to an approximate solution given limited accuracy data. We proceed with developing a multi-level algorithm based on a nested family of compact, convex subsets on which stability holds and the stability constants are ordered. Growth of the stability constants is coupled to the increase in accuracy of approximation between neighboring levels to ensure that the algorithm can continue from level to level until the iterate satisfies a desired discrepancy criterion, after a finite number of steps.
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Acknowledgments
The research was initiated at the Isaac Newton Institute for Mathematical Sciences (Cambridge, England) during a programme on Inverse Problems in Fall 2011. The authors would like to thank the anonymous referees for their valuable comments and suggestions to improve the quality of the paper.
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This research was supported in part National Science Foundation grant CMG DMS-1025318 and in part by the members of the Geo-Mathematical Imaging Group at Purdue University. The work of OS has been supported by the Austrian Science Fund (FWF) within the national research networks Photoacoustic Imaging in Biology and Medicine, project S10505 and Geometry and Simulation S11704.
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de Hoop, M.V., Qiu, L. & Scherzer, O. An analysis of a multi-level projected steepest descent iteration for nonlinear inverse problems in Banach spaces subject to stability constraints. Numer. Math. 129, 127–148 (2015). https://doi.org/10.1007/s00211-014-0629-x
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DOI: https://doi.org/10.1007/s00211-014-0629-x