  We describe a class of non-central extensions of the diffeomorphism algebra
in N-dimensional spacetime, and construct lowest-energy modules thereof, thus
generalizing work of Eswara-Rao and Moody. There is one representation for each
representation of $Vir\ltimes_{k_0}\km{gl(N)}$ (an extension of the semi-direct
product). Similar modules are constructed for gauge algebras.
