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Invariant fields of symplectic and orthogonal groups

✍ Scribed by David J. Saltman


Publisher
Elsevier Science
Year
2002
Tongue
English
Weight
271 KB
Volume
258
Category
Article
ISSN
0021-8693

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✦ Synopsis


The projective orthogonal and symplectic groups PO n (F ) and PSp n (F ) have a natural action on the F vector space

Here we assume F is an infinite field of characteristic not 2. If we assume there is more than one summand in V , then the invariant fields F (V ) PO n and F (V ) PSp n are natural objects. They are, for example, the centers of generic algebras with the appropriate kind of involution. This paper considers the rationality properties of these fields, in the case 1, 2, or 4 are the highest powers of 2 that divide n. We derive rationality when n is odd, or when 2 is the highest power, and stable rationality when 4 is the highest power. In a companion paper joint with Tignol, we prove retract rationality when 8 is the highest power of 2 dividing n. Back in this paper, along the way, we consider two generic ways of forcing a Brauer class to be in the image of restriction.


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