A formula for the logarithm of the KZ associator.
By using an invariant related to free Lie algebras, we give a criterion of non existence of isomorphism for the Pfaffian systems.
This project was partially supported by RFBR, grants 99-01-00233, 98-01-01020 and 00-15-96128.We study the asymptotic behaviour of numerical characteristics of polynomial identities of Lie algebras over a field of characteristic 0. In particular we investigate the colength for the cocharacters of polynilpotent varieties of Lie algebras. We prove that there exist polynilpotent Lie varieties with exponential and overexponential colength growth. We give the exact asymptotics for the colength of a product...
In this paper the problem of obstructions in Lie algebra deformations is studied from four different points of view. First, we illustrate the method of local ring, an alternative to Gerstenhaber’s method for Lie deformations. We draw parallels between both methods showing that an obstruction class corresponds to a nilpotent local parameter of a versal deformation of the law in the scheme of Jacobi. Then, an elimination process in the global ring, which defines the scheme, allows us to obtain nilpotent...
Si est une algèbre de Hopf commutative ou cocommutative et connexe, les puissances de convolution et le logarithme, au sens du produit de convolution, du morphisme identité de satisfont à diverses identités algébriques. L’algèbre de Hopf admet en particulier une décomposition en poids sous l’action des morphismes , dont nous étudions les propriétés.