Curious ill-posedness phenomena in the composition of non-compact linear operators in Hilbert spaces

Fuente: arXiv
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Autores principales: Kindermann, Stefan, Hofmann, Bernd
Formato: Preprint
Publicado: 2024
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author Kindermann, Stefan
Hofmann, Bernd
author_facet Kindermann, Stefan
Hofmann, Bernd
contents We consider the composition of operators with non-closed range in Hilbert spaces and how the nature of ill-posedness is affected by their composition. Specifically, we study the \mbox{Hausdorff-,} Cesàro-, integration operator, and their adjoints, as well as some combinations of those. For the composition of the Hausdorff- and the Cesàro-operator, we give estimates of the decay of the corresponding singular values. As a curiosity, this provides also an example of two practically relevant non-compact operators, for which their composition is compact. Furthermore, we characterize those operators for which a composition with a non-compact operator gives a compact one.
format Preprint
id arxiv_https___arxiv_org_abs_2401_14701
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Curious ill-posedness phenomena in the composition of non-compact linear operators in Hilbert spaces
Kindermann, Stefan
Hofmann, Bernd
Functional Analysis
We consider the composition of operators with non-closed range in Hilbert spaces and how the nature of ill-posedness is affected by their composition. Specifically, we study the \mbox{Hausdorff-,} Cesàro-, integration operator, and their adjoints, as well as some combinations of those. For the composition of the Hausdorff- and the Cesàro-operator, we give estimates of the decay of the corresponding singular values. As a curiosity, this provides also an example of two practically relevant non-compact operators, for which their composition is compact. Furthermore, we characterize those operators for which a composition with a non-compact operator gives a compact one.
title Curious ill-posedness phenomena in the composition of non-compact linear operators in Hilbert spaces
topic Functional Analysis
url https://arxiv.org/abs/2401.14701