An analogue of the Fourier transform is developed for D-algebras. G. Laumon
's equivalence between the derived category of D-modules on an abelian vari
ety and the derived category of G-modules on the universal extension of the
dual variety is seen as a degenerate case of a duality for twisted differe
ntial operators (tdo's) with respect to which the dual of a generic tdo is
again a tdo.