Geodesic
Positive Quadratic Forms on Intersections of Quadrics
Matematičeskie zametki, Tome 71 (2002) no. 1, pp. 27-36.

Voir la notice de l'article provenant de la source Math-Net.Ru

The positive definiteness of a quadratic form on the cone defined as the set of points at which given quadratic forms vanish or are nonnegative is studied. Necessary and sufficient conditions for the positivity of a quadratic form on this cone are obtained. The results are applied to study second-order sufficient conditions for abnormal extremal problems. 
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A. V. Arutyunov. Positive Quadratic Forms on Intersections of Quadrics. Matematičeskie zametki, Tome 71 (2002) no. 1, pp. 27-36. http://geodesic.mathdoc.fr/item/MZM_2002_71_1_a2/

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