#### DOCUMENTA MATHEMATICA, Vol. 22 (2017), 1-24

E. Bayer-Fluckiger and R. Parimala

Cohomological Invariants for G-Galois Algebras and Self-Dual Normal Bases

We define degree two cohomological invariants for \$G\$-Galois algebras over fields of characteristic not 2, and use them to give necessary conditions for the existence of a self--dual normal basis. In some cases (for instance, when the field has cohomological dimension \$\le 2\$) we show that these conditions are also sufficient.

2010 Mathematics Subject Classification:

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