Abstract
In a normed space we introduce an exact and approximate orthogonality relation connected with “norm derivatives” \({\rho^{\prime}_{\pm}}\) . We also consider classes of linear mappings preserving (exactly and approximately) this kind of orthogonality.
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Dedicated to Professor János Aczél on his 85th birthday
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Open Access This is an open access article distributed under the terms of the Creative Commons Attribution Noncommercial License (https://creativecommons.org/licenses/by-nc/2.0), which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
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Chmieliński, J., Wójcik, P. On a ρ-orthogonality. Aequat. Math. 80, 45–55 (2010). https://doi.org/10.1007/s00010-010-0042-1
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DOI: https://doi.org/10.1007/s00010-010-0042-1