New aspects of ill-posedness classification in Banach spaces

Fuente: arXiv
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Main Authors: Flemming, Jens, Hofmann, Bernd
Format: Preprint
Published: 2025
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author Flemming, Jens
Hofmann, Bernd
author_facet Flemming, Jens
Hofmann, Bernd
contents Motivated by a seminal paper of professor M. Z. Nashed published in 1987 on classification of ill-posed linear operator equations and distinguishing two types of ill-posedness in Banach and Hilbert spaces, we present, illustrate and justify a new classification scheme in this context. This scheme classifies bounded linear operators mapping between infinite-dimensional Banach spaces with respect to ill-posedness types, including non-injective operators that may have uncomplemented null-spaces. The hybrid case of strictly singular operators the range of which contains a closed infinite-dimensional subspace plays a prominent role there. By a series of new theorems we complement moreover the theory of $\ell^1$-regularization with respect to ill-posedness phenomena and shed some light on the role of weak*-to-weak continuity in the context of $\ell^1$-regularization for operators with uncomplemented null-space.
format Preprint
id arxiv_https___arxiv_org_abs_2511_06690
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle New aspects of ill-posedness classification in Banach spaces
Flemming, Jens
Hofmann, Bernd
Functional Analysis
47A52, 47B01
Motivated by a seminal paper of professor M. Z. Nashed published in 1987 on classification of ill-posed linear operator equations and distinguishing two types of ill-posedness in Banach and Hilbert spaces, we present, illustrate and justify a new classification scheme in this context. This scheme classifies bounded linear operators mapping between infinite-dimensional Banach spaces with respect to ill-posedness types, including non-injective operators that may have uncomplemented null-spaces. The hybrid case of strictly singular operators the range of which contains a closed infinite-dimensional subspace plays a prominent role there. By a series of new theorems we complement moreover the theory of $\ell^1$-regularization with respect to ill-posedness phenomena and shed some light on the role of weak*-to-weak continuity in the context of $\ell^1$-regularization for operators with uncomplemented null-space.
title New aspects of ill-posedness classification in Banach spaces
topic Functional Analysis
47A52, 47B01
url https://arxiv.org/abs/2511.06690