Recent Advances in Superstring Perturbation Theory

Recent advances made in the understading of the Ramond-Neveu-Schwarz formulation of superstring perturbation theory are reviewed. The role of chiral splitting, in terms of which a consistent GSO projected formula is obtained to all loop orders, is explained. Equivalence of the manifestly convariant Polyakov amplitudes with the manifestly unitary light-cone amplitudes is shown, thus establishing unitarity of the covariant approach and Lorentz invariance of the light-cone approach. Some implications for string theory and quantum gravity are pointed out.