Speaker: Andreas Schachner, University of Cambridge
Abstract: In this talk, I discuss three approaches to deriving and understanding α' effects in String Theory. I present preliminary results of a project on completing the ten-dimensional type II effective actions at higher order in string perturbation theory. In this context, I provide concrete evidence at the level of five-point superstring amplitudes that the kinematics in the maximally U(1)-violating sector is obtained from standard superspace integrals over sixteen fermionic coordinates. This is in line with 11D superparticle amplitudes in M-theory compactified on 2-tori where the well-known modular forms required for SL(2,Z) invariance of type IIB arise from integrating out winding modes on the torus.