Universality in string interactions

Understand

In this letter, we provide evidence for universality in the low-energy expansion of tree-level string interactions.

• More precisely, in the alpha'-expansion of tree-level scattering amplitudes, we conjecture that the leading transcendental coefficient at each order in alpha' is universal for all perturbative string theories.
• We have checked this universality up to seven points and trace its origin to the ability to restructure the disk integrals of open bosonic string into those of the superstring.
• The accompanying kinematic functions have the same low-energy limit and do not introduce any transcendental numbers in their alpha'-corrections.