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Article . 1995 . Peer-reviewed
License: Springer TDM
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image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao
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On Solèr's characterization of Hilbert spaces

Authors: Prestel, Alexander;

On Solèr's characterization of Hilbert spaces

Abstract

In her thesis [Commun. Algebra 23, No. 1, 219-243 (1995)], \textit{Maria Pia Solèr}, a student of the late H. Gross, proved that for every infinite dimensional hermitian space \((E, \langle\;\rangle)\) over a skew field \(K\) which is orthomodular, i.e. every subspace \(X\) of \(E\) satisfies \[ \text{if } X= (X^\perp )^\perp \quad \text{then} \quad E= X\oplus X^\perp, \tag{1} \] and which contains an orthonormal sequence \((e_n )_{n\in \mathbb{N}}\), necessarily \(K\) is \(\mathbb{R}\), \(\mathbb{C}\) or \(\mathbb{H}\) and \((E, \langle\;\rangle)\) is a Hilbert space over \(K\). In [\textit{H. A. Keller}, \textit{U. M. Künze} and \textit{M. P. Solèr}, `Orthomodular spaces' (to appear)] a simplification for the case of \(K\) being commutative is given. The aim of this paper is to present another simplification for the commutative case which carries over to the non-commutative case almost literally (see Section 5). The theorem we are going to prove first in the commutative case reads as follows: Theorem. Let \(K\) be a field, \({}^*: K\to K\) an involution on \(K\), \(E\) an infinite dimensional \(K\)-vector space, and \(\langle\;\rangle: E\times E\to K\) a hermitian form on \(E\). Then the only cases in which \((E,\langle\;\rangle)\) is orthomodular and contains an infinite orthonormal sequence \((e_n )_{n\in \mathbb{N}}\) occur if \((K,{}^*)= (\mathbb{R}, id)\) or \((\mathbb{C}, {}^-)\) and \((E,\langle\;\rangle)\) is a Hilbert space over \((K, {}^*)\). Although the proof given here is considerably shorter than the original one, it still uses the main ideas of M. P. Solèr.

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Germany
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Keywords

510.mathematics, Characterizations of Hilbert spaces, orthomodular, Article

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
10
Average
Top 10%
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