Some of the first examples of Hopf algebras described over a field k w x which are neither commutative nor cocommutative 13, 14 involve elements a and x which satisfy the relations ⌬ a s a m a, ⌬ x s x m a q 1 m x, and xa s qax Ž . Ž . for some q g k \_ 0. With the advent of quantum groups these re
Representations of Finite-Dimensional Hopf Algebras
✍ Scribed by Martin Lorenz
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 310 KB
- Volume
- 188
- Category
- Article
- ISSN
- 0021-8693
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✦ Synopsis
Let H denote a finite-dimensional Hopf algebra with antipode S over a field މ -.
w We give a new proof of the fact, due to Oberst and Schneider Manuscripta Math. 8 Ž .
x 1973 , 217᎐241 , that H is a symmetric algebra if and only if H is unimodular and S 2 is inner. If H is involutory and not semisimple, then the dimensions of all projective H-modules are shown to be divisible by char މ -. In the case where މ -is a splitting field for H, we give a formula for the rank of the Cartan matrix of H, reduced mod char މ -, in terms of an integral for H. Explicit computations of the Ž . Cartan matrix, the ring structure of G H , and the structure of the principal 0 indecomposable modules are carried out for certain specific Hopf algebras, in particular for the restricted enveloping algebras of completely solvable p-Lie Ž . algebras and of sl 2, މ -.
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