Low-Energy Effective Action of Superstring Theory

A fundamental task for the heterotic superstring theory is the determination of the effective action describing the physics of massless string excitations at low energies. This is necessary for the phenomenological applications of string theory, in particular for the unification of gauge interactions and for the gaugino condensation mechanism of supersymmetry breaking. In this talk, I report on the recent progress in computing the effective supergravity action from superstring scattering amplitudes, at the tree level and beyond. I discuss moduli-dependent string loop corrections to gauge and Yukawa couplings. Talk presented at the 7th Meeting of the American Physical Society Division of Particles and Fields, Fermilab, November 10-14, 1992