Relating one-loop string amplitudes with maximal versus reduced supersymmetry
Oliver Schlotterer (AEI, Potsdam-Golm)

In this talk, I will report on recent progress in the study of one-loop string amplitudes with half-maximal and quarter-maximal supersymmetry. The structure of massless one-loop amplitudes is argued to follow the patterns known from maximally supersymmetric cases with two additional legs. Inspired by the Feynman diagrams in their field-theory limit, I will explain the organizing principles of their tensor structure for external gauge bosons and gravitons. In particular, universal building blocks will be identified that apply to orbifold compactifications with both half-maximal and quarter-maximal supersymmetry.