Deformed Kac-Moody algebras and their representations

A class of Lie algebras S (A) associated to generalized Cartan matrices A is studied. The Lie algebras S(A) have much simpler structure than Kac-Moody algebras, but have the same root spaces with g(A). In particular, S(A) has an abelian subalgebra of "half size." We show that, S(A) has a non-degenerate invariant symmetric bilinear form if and only if A is symmetrizable; S(X-1) congruent to S(X-2) if and only if the GCMs X-1 and X-2 are the same up to a permutation of rows and columns. We study the lowest (respectively highest) weight Verma module (V) over bar(lambda) (respectively (V) over tilde (lambda)) over S(A), and obtain the necessary and sufficient conditions for (V) over bar(lambda) to be irreducible, and also find its maximal proper submodule when (V) over bar(lambda) is reducible. Then using graded dual module of (V) over bar(lambda) we deduce the necessary and sufficient conditions for (V) over tilde (lambda) to be irreducible. (C) 2008 Elsevier Inc. All rights reserved.