Geodesic
Twisted forms of classical groups
Algebra i analiz, Tome 34 (2022) no. 2, pp. 56-94

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A uniform description is given for the twisted forms of classical reductive group schemes. Such group schemes can be constructed via finite-dimensional algebraic objects, except in the cases of small rank. These objects, augmented odd form algebras, consist of nilpotent groups of class 2 with the action of the ground commutative ring, so we develop a theory of plane descent for them. In addition, classical isotropic reductive groups are described in terms of odd unitary groups up to isogeny.
Keywords: isotropic reductive groups, unitary groups. 
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E. Yu. Voronetskii. Twisted forms of classical groups. Algebra i analiz, Tome 34 (2022) no. 2, pp. 56-94. http://geodesic.mathdoc.fr/item/AA_2022_34_2_a1/

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