Abstract
We prove the following result for a not necessarily symmetrizable Kac–Moody algebra: Let x,y ∈ W with x ≥ y, and let λ ∈ P+. If n=l(x)-l(y), then Ext C(λ) n(M(x·λ),L(y·λ))=1.
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Neidhardt, W. A Result on Ext Over Kac–Moody Algebras. Algebras and Representation Theory 1, 161–168 (1998). https://doi.org/10.1023/A:1009933409824
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DOI: https://doi.org/10.1023/A:1009933409824