Abstract
Two different proofs are given showing that a quaternion algebra Q defined over a quadratic étale extension K of a given field has a corestriction that is not a division algebra if and only if Q contains a quadratic algebra that is linearly disjoint from K. This is known in the case of a quadratic field extension in characteristic different from two. In the case where K is split, the statement recovers a well-known result on biquaternion algebras due to Albert and Draxl.
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Karim Johannes Becher was supported by the FWO Odysseus Programme (project Explicit Methods in Quadratic Form Theory), funded by the Fonds Wetenschappelijk Onderzoek – Vlaanderen. Jean-Pierre Tignol acknowledges support from the Fonds de la Recherche Scientifique–FNRS under Grants Nos. J.0014.15 and J.0149.17.
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Becher, K.J., Grenier-Boley, N. & Tignol, JP. Transfer of quadratic forms and of quaternion algebras over quadratic field extensions. Arch. Math. 111, 135–143 (2018). https://doi.org/10.1007/s00013-018-1198-5
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DOI: https://doi.org/10.1007/s00013-018-1198-5