# On fields of u-invariant 4

Authors
• 1 École Polytechnique Fédérale de Lausanne, Lausanne, CH - 1015, Switzerland , Lausanne (Switzerland)
Type
Published Article
Journal
Archiv der Mathematik
Publisher
Birkhäuser-Verlag
Publication Date
Jan 01, 2006
Volume
86
Issue
1
Pages
31–35
Identifiers
DOI: 10.1007/s00013-005-1491-y
Source
Springer Nature
Keywords
This note is motivated by the problem of determining the u-invariant of a field F of characteristic different from two when it is known that \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$u\left( {F\left( {\sqrt { - 1} } \right)} \right) = 4.$$\end{document} A criterion is given to decide whether u(F) ≤ 4 in this situation.