Journal Home Page Cumulative Index List of all Volumes Complete Contentsof this Volume Previous Article Journal of Lie Theory 20 (2010), No. 4, 673--687Copyright Heldermann Verlag 2010 Principal Basis in Cartan Subalgebra Rudolf Philippe Rohr Dept. of Mathematics, University of Geneva, 2-4 rue de Lievre / C.P.64, 1211 Geneva 4, Switzerland Rudolf.Rohr@unige.ch [Abstract-pdf] \def\g{{\frak g}} \def\h{{\frak h}} Let $\g$ be a simple complex Lie algebra and $\h$ a Cartan subalgebra. In this article we explain how to obtain the principal basis of $\h$ starting form a set of generators $\{p_1, \cdots ,p_r\}$,$r={\rm rank}(\g)$, of the invariants polynomials $S(\g^*)\g$. For each invariant polynomial $p$, we define a $G$-equivariant map $Dp$ form $\g$ to $\g$. We show that the Gram-Schmidt orthogonalization of the elements $\{Dp_1(\rho^\vee), \cdots Dp_r(\rho^\vee)\}$ gives the principal basis of $\h$. Similarly the orthogonalization of the elements $\{Dp_1(\rho), \cdots, Dp_r(\rho)\}$ produces the principal basis of the Cartan subalgebra of $\g^\vee$, the Langlands dual of $\g$. Keywords: Lie algebra, Cartan subalgebra, principal basis, Langlands dual. MSC: 17B [ Fulltext-pdf  (204  KB)] for subscribers only.