Preprint
Higher extensions between modules for SL_2
Alison Parker
Abstract
We calculate Ext^*_{SL_2(k)}(Δ(λ), Δ(μ)),
Ext^*_{SL_2(k)}(L(λ), Δ(μ)),
Ext^*_{SL_2(k)}(Δ(λ), L(μ)), and
Ext^*_{SL_2(k)}(L(λ), L(μ)), where Δ(λ)
is the Weyl module of highest weight λ, L(λ) is
the simple SL_2(k)module of highest weight λ and our
field k is algebraically closed of positive characteristic. We
also get analogous results for the DipperDonkin quantisation.
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Friday, September 24, 2004 
