Submission: 2008, Aug 29
The generic quadratic form of even dimension n with trivial discriminant over an arbitrary field of characteristic different from 2 containing a square root of -1 can be written in the Witt ring as a sum of 2-fold Pfister forms using n-2 terms and not less. The number of 2-fold Pfister forms needed to express a quadratic form of dimension 6 with trivial discriminant is determined in various cases.
2000 Mathematics Subject Classification: 11E04, 11E81
Keywords and Phrases: quadratic forms, Pfister numbers.
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