Geodesic
A Note on Quadratic Forms and the u-invariant
Canadian journal of mathematics, Tome 26 (1974) no. 5, pp. 1242-1244

Voir la notice de l'article provenant de la source Cambridge University Press

The u-invariant of a field F, u = u(F), is defined to be the maximum of the dimensions of anisotropic quadratic forms over F. If F is a non-formally real field with a finite number q of square classes then it is known that u ≦ q. The purpose of this note is to give some necessary and sufficient conditions for equality in terms of the structure of the Witt ring of F. 
Ware, Roger. A Note on Quadratic Forms and the u-invariant. Canadian journal of mathematics, Tome 26 (1974) no. 5, pp. 1242-1244. doi: 10.4153/CJM-1974-118-0
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