The converse to Karpenko's non-ruledness theorem for anisotropic quadratic forms

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Let qq be an anisotropic quadratic form over a field kk. Its first Witt index is the Witt index of qq after extending scalars to the function field of the projective quadric defined by qq, and qq is ruled over kk when its projective quadric is ruled.

Converse to Karpenko's theorem. If the first Witt index of qq is greater than 11, then qq is ruled over kk.

Karpenko's theorem says that an anisotropic quadratic form with first Witt index 11 is not ruled. This conjecture proposes the converse and is supported in the source by a proof for quadratic forms of dimension at most 99.

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Sources & referencesView supporting material

Primary source

Burt Totaro, “The automorphism group of an affine quadric”, arXiv:math/0608094 (2006).

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