Actions of Hopf algebras on fully bounded Noetherian rings.
Actions of Hopf algebras on pro-semisimple noetherian algebras and their invariants
Let H be a Hopf algebra over a field k such that every finite-dimensional (left) H-module is semisimple. We give a counterpart of the first fundamental theorem of the classical invariant theory for locally finite, finitely generated (commutative) H-module algebras, and for local, complete H-module algebras. Also, we prove that if H acts on the k-algebra A = k[[X₁,...,Xₙ]] in such a way that the unique maximal ideal in A is invariant, then the algebra of invariants is a noetherian Cohen-Macaulay...
Addendum to “Hochschild cohomology of skew group rings and invariants”
Constructing invariants for finite groups.
Global structure of the mod two symmetric algebra, over the Steenrod Algebra.
Hochschild Cohomology of skew group rings and invariants
Let A be a k-algebra and G be a group acting on A. We show that G also acts on the Hochschild cohomology algebra HH ⊙ (A) and that there is a monomorphism of rings HH ⊙ (A) G→HH ⊙ (A[G]). That allows us to show the existence of a monomorphism from HH ⊙ (Ã) G into HH ⊙ (A), where à is a Galois covering with group G.
Hochschild homology and cohomology of generalized Weyl algebras
We compute Hochschild homology and cohomology of a class of generalized Weyl algebras, introduced by V. V. Bavula in St. Petersbourg Math. Journal, 4 (1) (1999), 71-90. Examples of such algebras are the n-th Weyl algebras, , primitive quotients of , and subalgebras of invariants of these algebras under finite cyclic groups of automorphisms. We answer a question of Bavula–Jordan (Trans. A.M.S., 353 (2) (2001), 769-794) concerning the generators of the group of automorphisms of a generalized Weyl...
Homogeneous polynomials with isomorphic Milnor algebras
We recall first Mather's Lemma providing effective necessary and sufficient conditions for a connected submanifold to be contained in an orbit. We show that two homogeneous polynomials having isomorphic Milnor algebras are right-equivalent.
Homology of invariants of a Weyl algebra under a finite group action. (Homologie des invariants d'une algèbre de Weyl sous l'action d'un groupe fini.)
Invariants of Unipotent Transformations Acting on Noetherian Relatively Free Algebras
2000 Mathematics Subject Classification: 16R10, 16R30.The classical theorem of Weitzenböck states that the algebra of invariants K[X]^g of a single unipotent transformation g ∈ GLm(K) acting on the polynomial algebra K[X] = K[x1, . . . , xm] over a field K of characteristic 0 is finitely generated.Partially supported by Grant MM-1106/2001 of the Bulgarian National Science Fund.
On Azumaya Galois extensions and skew group rings.
On central commutator Galois extensions of rings.
On certain classes of Galois extensions of rings.
On characterizations of a center Galois extension.
On Splitting Rings for Azumaya Skew Group Rings
Projectivity and flatness over the endomorphism ring of a finitely generated module.
Second order differential invariants of linear frames.
Sur quelques théorèmes fondamentaux de l'algèbre moderne
The basic construction from the conditional expectation on the quantum double of a finite group
Let be a finite group and a subgroup. Denote by (or ) the crossed product of and (or ) with respect to the adjoint action of the latter on the former. Consider the algebra generated by and , where we regard as an idempotent operator on for a certain conditional expectation of onto . Let us call the basic construction from the conditional expectation . The paper constructs a crossed product algebra , and proves that there is an algebra isomorphism between and .
The geometric reductivity of the quantum group
We introduce the concept of geometrically reductive quantum group which is a generalization of the Mumford definition of geometrically reductive algebraic group. We prove that if G is a geometrically reductive quantum group and acts rationally on a commutative and finitely generated algebra A, then the algebra of invariants is finitely generated. We also prove that in characteristic 0 a quantum group G is geometrically reductive if and only if every rational G-module is semisimple, and that in...