Abstract
We study totally decomposable symplectic and unitary involutions on central simple algebras of index 2 and on split central simple algebras respectively. We show that for every field extension, these involutions are either anisotropic or hyperbolic after extending scalars, and that the converse holds if the algebras are of 2-power degree. These results are new in characteristic 2, otherwise the symplectic result was shown in Becher (Invent Math 173(1):1–6, 2008) and the unitary result was partly shown in Black and Quéguiner-Mathieu (Enseign Math 60(3–4):377–395, 2014).
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This work was supported by the DFG (The Pfister Factor Conjecture in Characteristic Two, BE 2614/4) and the FWO Odysseus programme (Explicit Methods in Quadratic Form Theory).
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Dolphin, A. Totally decomposable symplectic and unitary involutions. manuscripta math. 153, 523–534 (2017). https://doi.org/10.1007/s00229-016-0891-6
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DOI: https://doi.org/10.1007/s00229-016-0891-6