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The classical Jacobson-Morosov theorem states that over a field k of
characteristic zero, the embedding of the additive group Ga into
SL2
is universal among homomorphisms from Ga to a reductive group, in the sense
that any such homomorphism factors through the embedding, and any two
factorisations are conjugate.
Based on a categorical splitting theorem, Andre and Kahn proved that a similar universal property holds with Ga replaced by an arbitrary algebraic group over k and SL2 by an appropriate limit of reductive groups. In this talk a more geometric approach to this result will be given, using actions of reductive groups on affine schemes. After the seminar we will take the speaker to lunch. See the Algebra Seminar web page for information about other seminars in the series. Anthony Henderson anthonyh@maths.usyd.edu.au. |