Preface . . . . . . . . . . . . . . . . . . . . . . . iii 1. Rings and Ideals . . . . . . . . . . . . . . . . . . . 1 2. Prime Ideals . . . . . . . . . . . . . . . . . . . . 6 3. Radicals . . . . . . . . . . . . . . . . . . . . . . 10 4. Modules . . . . . . . . . . . . . . . . . . . . . . 14 5. Exact Sequences . . . . . . . . . . . . . . . . . . . 20 6. Direct Limits . . . . . . . . . . . . . ....

A current Lie algebra is contructed from a tensor product of a Lie algebra and a commutative associative algebra of dimension greater than 2. In this work we are interested in deformations of such algebras and in the problem of rigidity. In particular we prove that a current Lie algebra is rigid if it is isomorphic to a direct product g× g × ...× g where g is a rigid Lie algebra. 1 Current Lie ...

We introduce a new formalism of differential operators for a general associative algebra A. It replaces Grothendieck’s notion of differential operator on a commutative algebra in such a way that derivations of the commutative algebra are replaced by DerA, the bimodule of double derivations. Our differential operators act not on the algebra A itself but rather on F(A), a certain ‘Fock space’ ass...

This paper extends classical results in the invariant theory of finite groups and finite group schemes to the actions of finite Hopf algebras on commutative rings. Suppose that H is a finite dimensional Hopf algebra and A a commutative algebra, say over a field K. Let δ : A → A ⊗H be an algebra homomorphism which makes A into a right H-comodule. In this case A is called an H-comodule algebra. T...