These lectures given in Montreal in Summer 1997 are mainly based on, and form a condensed survey of the book N. Chriss, V. Ginzburg ‘Representation Theory and Complex Geometry’ , Birkhäuser 1997. Various algebras arising naturally in Representation Theory such as the group algebra of a Weyl group, the universal enveloping algebra of a complex semisimple Lie algebra, a Quantum group or the Iwaho...

Hochschild cohomology governs deformations of algebras, and its graded Lie structure plays a vital role. We study this structure for the Hochschild cohomology of the skew group algebra formed by a finite group acting on an algebra by automorphisms. We examine the Gerstenhaber bracket with a view toward deformations and developing bracket formulas. We then focus on the linear group actions and p...

We consider a class of infinite-dimensional Lie algebras which is associated to dynamical systems with invariant measures. There are two constructions of the algebras – one based on the associative cross product algebra which considered as Lie algebra and then extended with nontrivial scalar twococycle; the second description is the specification of the construction of the graded Lie algebras w...

Nekrashevych algebras of self-similar group actions are natural generalizations the classical Leavitt algebras. They discrete analogues corresponding $$C^*$$ -algebras. In particular, Nekrashevych, Clark, Exel, Pardo, Sims and Starling have studied question simplicity algebras, in part, because non-simplicity complex algebra implies -algebra. this paper we give necessary sufficient conditions f...

Hochschild cohomology governs deformations of algebras, and its graded Lie structure plays a vital role. We study this structure for the Hochschild cohomology of the skew group algebra formed by a finite group acting on an algebra by automorphisms. We examine the Gerstenhaber bracket with a view toward deformations and developing bracket formulas. We then focus on the linear group actions and p...

Abstract. The normal symmetric triality algebras (STA’s) and the normal Lie related triple algebras (LRTA’s) have been recently introduced by the second author, in connection with the principle of triality. It turns out that the unital normal LRTA’s are precisely the structurable algebras extensively studied by Allison. It will be shown that the normal STA’s (respectively LRTA’s) are the algebr...

The purpose of this paper is to introduce a cohomology theory for abelian matched pairs of Hopf algebras and to explore its relationship to Sweedler cohomology, to Singer cohomology and to extension theory. An exact sequence connecting these cohomology theories is obtained for a general abelian matched pair of Hopf algebras, generalizing those of Kac and Masuoka for matched pairs of finite grou...