World-sheet versus spectrum symmetries in heterotic and type II superstrings

We discuss the relation between world-sheet symmetries of general four-dimensional superstring theories and the classification of their massless and massive excitations. This follows from the connection between extended superconformal algebras on the world-sheet and extended space-time supersymmetry algebras. In particular we show that the relevant Kac-Moody symmetries are extended to the spectrum symmetries of the supermultiplets of states. This analysis reproduces results for the field theory limit of superstring compactifications