Totally real closures of fields of formally real fields

Authors
Citation
B. Deschamps, Totally real closures of fields of formally real fields, MANUSC MATH, 100(3), 1999, pp. 291-304
Citations number
12
Categorie Soggetti
Mathematics
Journal title
MANUSCRIPTA MATHEMATICA
ISSN journal
00252611 → ACNP
Volume
100
Issue
3
Year of publication
1999
Pages
291 - 304
Database
ISI
SICI code
0025-2611(199911)100:3<291:TRCOFO>2.0.ZU;2-Z
Abstract
This article is concerned with arithmetic properties of totally real closur es of formally real fields. We generalize previous results of Fried, Volkle in and Pop to show that if an algebraic extension K/Q is formally real and hilbertian then the absolute Galois group of the cyclotomic closure of the totally real closure of K is pro-free. In addition, we give a precise descr iption of the Brauer group of (K) over tilde(tr): it is always an elementar y abelian 2-group. Finally, using a result of Glass and Ribenboim, we show that an automorphism of the group Aut((K) over tilde(tr)(+)*, less than or equal to 1..), where K is a formally real number field, is necessarily the identity.