Characterizations of smooth spaces by approximate orthogonalities

Verfasser / Beitragende:
[Paweł Wójcik]
Ort, Verlag, Jahr:
2015
Enthalten in:
Aequationes mathematicae, 89/4(2015-08-01), 1189-1194
Format:
Artikel (online)
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024 7 0 |a 10.1007/s00010-014-0293-3  |2 doi 
035 |a (NATIONALLICENCE)springer-10.1007/s00010-014-0293-3 
100 1 |a Wójcik  |D Paweł  |u Institute of Mathematics, Pedagogical University of Cracow, Podchor֥ażych 2, 30-084, Kraków, Poland  |4 aut 
245 1 0 |a Characterizations of smooth spaces by approximate orthogonalities  |h [Elektronische Daten]  |c [Paweł Wójcik] 
520 3 |a Since the monograph by Amir that appeared in 1986, a lot of attention has been given to the problem of characterizing, by means of properties of the norms, when a Banach space is indeed a Hilbert space, i.e., when the norm derives from an inner product. In this paper, similar investigations will be carried out for smooth spaces instead of inner product spaces. We consider the approximate orthogonalities in real normed spaces. We show that the relations approximate semi-orthogonality and approximate ρ+-orthogonality are generally incomparable (unless the normed space is smooth). As a result, we give a characterization of smooth spaces in terms of those approximate orthogonalities. 
540 |a The Author(s), 2014 
690 7 |a Approximate orthogonality  |2 nationallicence 
690 7 |a Smoothness  |2 nationallicence 
690 7 |a Norm derivative  |2 nationallicence 
690 7 |a Semi-inner product  |2 nationallicence 
773 0 |t Aequationes mathematicae  |d Springer Basel  |g 89/4(2015-08-01), 1189-1194  |x 0001-9054  |q 89:4<1189  |1 2015  |2 89  |o 10 
856 4 0 |u https://doi.org/10.1007/s00010-014-0293-3  |q text/html  |z Onlinezugriff via DOI 
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900 7 |a Metadata rights reserved  |b Springer special CC-BY-NC licence  |2 nationallicence 
908 |D 1  |a research-article  |2 jats 
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950 |B NATIONALLICENCE  |P 856  |E 40  |u https://doi.org/10.1007/s00010-014-0293-3  |q text/html  |z Onlinezugriff via DOI 
950 |B NATIONALLICENCE  |P 100  |E 1-  |a Wójcik  |D Paweł  |u Institute of Mathematics, Pedagogical University of Cracow, Podchor֥ażych 2, 30-084, Kraków, Poland  |4 aut 
950 |B NATIONALLICENCE  |P 773  |E 0-  |t Aequationes mathematicae  |d Springer Basel  |g 89/4(2015-08-01), 1189-1194  |x 0001-9054  |q 89:4<1189  |1 2015  |2 89  |o 10