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arXiv 2005.14674math.NAcs.NA
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$\ell^1$ -正则化中逼近速度的极大空间

Maximal Spaces for Approximation Rates in $\ell^1$-regularization

Philip Miller, Thorsten Hohage

摘要:

本文研究了具有加权$\ell^1$ -惩罚的可能非线性反问题的Tikhonov正则化。从数列空间映射到任意Banach空间的前向算子,通常是$L^2$ -空间,被假定满足关于加权$\ell^2$ -范数和像空间范数的双边利普希茨条件.我们表明,在这种设置的逼近率的任意高的Hölder型顺序的正则化参数可以实现,我们的特点是最大的子空间序列上,这些速度达到。在这些子空间上,该方法也收敛于最佳速率的噪声水平与差异原则作为参数选择规则。我们的分析包括惩罚项在精确解上不是有限的情况(“过平滑”).作为一个标准的例子,我们讨论小波正则化Besov空间$B^r_{1,1}$。在这种情况下,我们证明在数值模拟的参数识别问题的微分方程,我们的理论结果正确地预测改进的分段光滑未知系数的收敛速度。

英文摘要:

We study Tikhonov regularization for possibly nonlinear inverse problems with weighted $\ell^1$-penalization. The forward operator, mapping from a sequence space to an arbitrary Banach space, typically an $L^2$-space, is assumed to satisfy a two-sided Lipschitz condition with respect to a weighted $\ell^2$-norm and the norm of the image space. We show that in this setting approximation rates of arbitrarily high Hölder-type order in the regularization parameter can be achieved, and we characterize maximal subspaces of sequences on which these rates are attained. On these subspaces the method also converges with optimal rates in terms of the noise level with the discrepancy principle as parameter choice rule. Our analysis includes the case that the penalty term is not finite at the exact solution ('oversmoothing'). As a standard example we discuss wavelet regularization in Besov spaces $B^r_{1,1}$. In this setting we demonstrate in numerical simulations for a parameter identification problem in a differential equation that our theoretical results correctly predict improved rates of convergence for piecewise smooth unknown coefficients.

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