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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 Mathematische Zeitsc...arrow_drop_down
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
Mathematische Zeitschrift
Article . 1990 . Peer-reviewed
License: Springer TDM
Data sources: Crossref
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
zbMATH Open
Article . 1990
Data sources: zbMATH Open
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Formally real fields, pythagorean fields,C-fields andW-groups

Formally real fields, pythagorean fields, C-fields and W-groups
Authors: Minác, Ján; Spira, Michel;

Formally real fields, pythagorean fields,C-fields andW-groups

Abstract

In previous work the authors showed that under some mild condition on the field F the Galois group \({\mathcal G}_ F\) of a certain 2-extension \(F^{(3)}\) of F completely determines the Witt ring of F. In this paper it is shown that the presence or absence of certain involutions in \({\mathcal G}_ F\) determines whether F is a formally real field or not. More precisely a 1-1 correspondence is shown between orderings of fields and certain classes of involutions in \({\mathcal G}_ F\). The relative real closure of a formally real field F inside of \(F^{(3)}\) is defined and this is used to give a new characterization of superpythagorean fields. Moreover a characterization of pythagorean fields via \({\mathcal G}_ F\) is shown as well as the description of all possible Abelian groups \({\mathcal G}_ F\). The main tools are dihedral and \({\mathbb{Z}}/4 {\mathbb{Z}}\) extensions, together with simple Galois theory. This paper can be viewed as transfer of classical results of Artin- Schreier and Becker to much smaller fields.

Country
Germany
Keywords

superpythagorean fields, Ordered fields, Separable extensions, Galois theory, Article, formally real field, relative real closure, 510.mathematics, orderings of fields, Witt ring, involutions in Galois groups, Fields related with sums of squares (formally real fields, Pythagorean fields, etc.), Algebraic theory of quadratic forms; Witt groups and rings, pythagorean fields, Forms over real fields

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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!
12
Average
Top 10%
Average
Green