Demazure, lectures on p-divisible groups, III.4, duality of finite Witt groups
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Definition and Remark
For , let be the set of all such that for large , and nilpotent for all .
is an ideal in .
is a polynomial for .
In particular is defined for , and we have a morphism of groups
If , then and . (…)
is bilinear and hence gives a morphism of groups
which is an isomorphism.
be the section of .
is not a morphism of groups. sends in .
For , , define
then is bilinear and gives an isomorphism