Generalized Demazure modules and fusion products

Let g be a finite-dimensional complex simple Lie algebra with highest root θ and let g[t] be the corresponding current algebra. In this paper, we consider the g[t]-stable Demazure modules associated to integrable highest weight representations of the affine Lie algebra gˆ. We prove that the fusion product of Demazure modules of a given level with a single Demazure module of a different level and with highest weight a multiple of θ is a generalized Demazure module, and also give defining relations. This also shows that the fusion product of such Demazure modules is independent of the chosen parameters. As a consequence we obtain generators and relations for certain types of generalized Demazure modules. We also establish a connection with the modules defined by Chari and Venkatesh.