On Ol'shanskii's semigroup.
We use categories to recast the combinatorial theory of full heaps, which are certain labelled partially ordered sets that we introduced in previous work. This gives rise to a far simpler set of definitions, which we use to outline a combinatorial construction of the so-called loop algebras associated to affine untwisted Kac--Moody algebras. The finite convex subsets of full heaps are equipped with a statistic called parity, and this naturally gives rise to Kac's asymmetry function. The latter is...
We study the invariants of the universal enveloping algebra of a Lie superalgebra with respect to a certain “twisted” adjoint action.
Let denote the class of nilpotent Lie algebras. For any finite-dimensional Lie algebra over an arbitrary field , there exists a smallest ideal of such that . This uniquely determined ideal of is called the nilpotent residual of and is denoted by . In this paper, we define the subalgebra . Set . Define for . By denote the terminal term of the ascending series. It is proved that if and only if is nilpotent. In addition, we investigate the basic properties of a Lie algebra...
We define Witten multiple zeta-functions associated with semisimple Lie algebras , of several complex variables, and prove the analytic continuation of them. These can be regarded as several variable generalizations of Witten zeta-functions defined by Zagier. In the case , we determine the singularities of this function. Furthermore we prove certain functional relations among this function, the Mordell-Tornheim double zeta-functions and the Riemann zeta-function. Using these relations, we prove...