Hostname: page-component-8448b6f56d-c4f8m Total loading time: 0 Render date: 2024-04-20T00:09:59.134Z Has data issue: false hasContentIssue false

Geometric Characterizations of Hilbert Spaces

Published online by Cambridge University Press:  20 November 2018

Francisco Javier García-Pacheco
Affiliation:
Department of Mathematics, Universidad de Cádiz, Cadiz, Spain e-mail: garcia.pacheco@uca.es
Justin R. Hill
Affiliation:
Temple College, Temple, Texas, USA e-mail: hillj116@templejc.edu
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

We study some geometric properties related to the set

$${{\Pi }_{X}}\,:=\left\{ \left( x,\,{{x}^{*}} \right)\,\in \,{{\text{S}}_{X}}\,\times \,{{\text{S}}_{{{X}^{*}}}}\,:\,{{x}^{*}}\left( x \right)\,=\,1 \right\}$$

obtaining two characterizations of Hilbert spaces in the category of Banach spaces. We also compute the distance of a generic element $\left( h,\,k \right)\,\in \,H\,{{\oplus }_{2}}\,H$ to ${{\Pi }_{H}}$ for $H$ a Hilbert space.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2016

References

[1] Aizpuru, A. and Garcia-Pacheco, E J., L -summand vectors in Banach spaces.Vroc. Amer. Math. Soc. 134(2006), no. 7, 21092115. http://dx.doi.Org/10.1090/S0002-9939-06-08243-8 Google Scholar
[2] Chica, M., Kadets, V., Martin, M., Moreno-Pulido, S., and Rambla-Barreno, R, Bishop-Phelps-Bollobds moduli of a Banach space. J. Math. Anal. Appl. 412(2014), 697719. http://dx.doi.Org/10.1016/j.jmaa.2O13.10.083 Google Scholar
[3] Deville, R., Godefroy, G., and Zizler, V., Smoothness and renormings in Banach spaces. Pitman Monographs and Surveys in Pure and Applied Mathematics 64, Longman Scientific & Technical, New York, 1993.Google Scholar
[4] Kadets, V., Martin, M., and Paya, R., Recent progress and open questions on the numerical index of Banach spaces. RACSAM Rev. R. Acad. Cienc. Exactas Fis. Nat. Ser. A Mat. 100(2006), no. 1-2, 155182.Google Scholar