
doi: 10.1007/bf02571260
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.
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
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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