Combinatorics and Topology of Kawai-Lewellen-Tye Relations

Understand

We revisit the relations between open and closed string scattering amplitudes discovered by Kawai, Lewellen, and Tye (KLT).

• We show that they emerge from the underlying algebro-topological identities known as the twisted period relations.
• In order to do so, we formulate tree-level string theory amplitudes in the language of twisted de Rham theory.
• There, open string amplitudes are understood as pairings between twisted cycles and cocycles.